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M980175UNFINAL7A.doc.DOC

Corrosion Detection Technologies

Sector Study

FINAL REPORT

Prepared for the

North American Technology and Industrial Base Organization

(NATIBO)

Prepared by BDM Federal, Inc.


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DISCLAIMER

The mention of specific products or companies does not constitute an endorsement byBDM, the U.S. Government, the Canadian Government, or the Australian Government. Use ofthe information contained in this publication shall be with the user’s understanding that neitherBDM, nor the three Governments, by the inclusion or exclusion of any company in thisdocument, provides any endorsement or opinion as to the included or excluded companies’products, capabilities, or competencies. The list of companies contained in this document is notrepresented to be complete or inclusive.


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FOREWORD

In February 1996, the North American Technology and Industrial Base Organization’s(NATIBO) Steering Group commissioned a study of corrosion detection technologies and theirimplementation throughout North America’s defense and commercial industrial bases.

This report provides the results of the study of corrosion detection technologies, which wasconducted between March 1997 and March 1998. It gives a complete and thorough analysis ofpresent and emerging corrosion detection technologies and the industry outlook for thesetechnologies; highlights land, sea, and air applications of corrosion detection technologies;identifies corrosion detection proponents, equipment developers, and researchers in government,industry, and academia; and pinpoints barriers and impediments blocking the expansion ofcorrosion detection technologies into the industrial base. From this analysis, the report provides aroadmap of recommendations for government and/or industry action to eliminate barriers andaddress issues hindering more widespread use of these technologies.

This report was prepared for the NATIBO by BDM Federal, Inc. (BDM), 1501 BDM Way,McLean, VA 22102.


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ACKNOWLEDGMENTS

The authors would like to express their appreciation to the many individuals whosecooperation in providing essential information made this effort possible. This study could nothave been completed without the dedicated efforts of the North American Technology andIndustrial Base Organization Corrosion Detection Technologies Working Group members(including Australia), listed here in alphabetical order:

Major Dennis Clark Directorate Defense Research and Engineering

Ms. Cynthia Gonsalves Directorate Defense Research and Engineering

Mr. Michael Ives Embassy of Australia

Ms. Julie Jacks Marine Corps Systems Command

Mr. Al Moore Air Force Research Laboratory

Mr. Bryan Prosser Marine Corps Systems Command

Mr. Dilip Punatar Air Force Research Laboratory

Mr. Arthur D. Schatz Embassy of Australia

Mr. Michael Slack Canadian Department of National Defence

Mr. Rod White U.S. Army Industrial Engineering Activity

Commander Spence Witten Office of Naval Research

The authors would also like to express their appreciation to the many companies, governmentagencies, and academic institutions who supplied us with timely, important informationnecessary to conduct this assessment:

Aging Aircraft Nondestructive InspectionSystem Validation Center at Sandia

Aging Aircraft Office

Aerospace and TelecommunicationsEngineering Support Squadron

Air Canada

Air Force Office of Scientific Research

Air Vehicle Research Detachment

Aloha Airlines

Army Aviation Missile Command

Army Research Laboratory

Boeing

Carnegie Mellon Research Institute

Center for Aviation System Reliability atIowa State University

College of William and Mary

Corpus Christi Army Depot

C. W. Pope & Associates

Defence Science and Technology Office

Diffracto

Engineering Testing and Research Services

FAA Airworthiness Center

FAA Hughes Technical Center

Jacksonville Naval Aviation Depot


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Jet Propulsion Laboratory

Johns Hopkins University

Kennedy Space Center

Lawrence Berkeley Laboratory

Lawrence Livermore National Laboratory

Lewis Research Center

MARCORSYSCOM

McDonnell Douglas

Mid-Atlantic Regional Maintenance Facility

NASA Kennedy Space Center

NASA Langley Research Center

National Research Council Canada/Institute for Aerospace Research

Naval Air Systems Command

Naval Research Laboratory

Naval Surface Warfare Center

NIST

North Island, NAVAIR

Northwest Airlines

Northwestern University

NSWC-Carderock

Oklahoma City ALC

Office of Naval Research

Pearl Harbor Naval Shipyard

Penn State University

Picatinny Arsenal

PRI Instrumentation, Inc.

Qantas

Quality Engineering Test Establishment

RAAF Amberley

RAAF Richmond

RAAF Williamtown

Royal Australian Air Force

Royal Military College

Sacramento ALC

San Antonio ALC

Southwest Research Institute

TACOM

Thermal Wave Imaging, Inc.

Tektrend International

TPL, Inc.

UCLA

University of Dayton Research Institute

University of Pennsylvania

University of Washington

U.S. Army Pacific

U.S. Coast Guard

Utex Scientific Instruments

Warner Robins ALC

Wayne State University

Wright Laboratories/AFRL

M980175UN ES-1EXSUM3A.doc

ES.1. EXECUTIVE SUMMARY

ES.1.1 Introduction

The North American Technology and Industrial Base Organization (NATIBO) undertookthis corrosion detection technologies study to assess the industrial base, maturity, level of use,utility, and viability of corrosion detection technologies for land, air and sea applications. Fromthis analysis, conclusions regarding these technologies and their further commercialization arediscussed. The recommendations addressing these conclusions are then provided for potentialfuture action. Joining the NATIBO in this effort for the first time is the Australian Departmentof Defence.

ES.1.2 Technology Overview

ES.1.2.1 Corrosion FundamentalsCorrosion of metal in military systems is a highly complex phenomenon and takes many

different forms. The result of all corrosion is the loss of strength of the material and the structure.Understanding the various forms and combinations of corrosion is essential to determining theimportance of each and to finding the most appropriate technologies for detection andcharacterization of corrosion.

The following table summarizes the types of corrosion that can damage structures and theircharacteristics.

Table ES-1. Corrosion Types and Characteristics.

CorrosionType

Cause Appearance By-Product

UniformAttack

Exposure to corrosiveenvironment

Irregular roughening of theexposed surface

Scale, metallic salts

Pitting Impurity or chemicaldiscontinuity in the paintor protective coating

Localized pits or holes withcylindrical shape andhemispherical bottom

Rapid dissolution of thebase metal

Inter-granular orExfoliation

Presence of strong potentialdifferences in grain or phaseboundaries

Appears at the grain orphase boundaries as uniformdamage

Produces scale typeindications at smallermagnitude than stresscorrosion

Crevice Afflicts mechanical joints,such as coupled pipes orthreaded connections.Triggered by localdifference in environmentcomposition (Oxygenconcentration)

Localized damage in theform of scale and pitting

Same as scale and pitting


CorrosionType


Filiform High humidity aroundfasteners, skin joints orbreaks in coating cause anelectrolytic process

Fine, meandering, thread-liketrenches that spread fromthe source

Similar to scale. Liftingof the coating.

GalvanicCorrosion

Corrosive condition thatresults from contact ofdifferent metals

Uniform damage, scale,surface fogging or tarnishing

Emission of mostlymolecular hydrogen gasin a diffused form

StressCorrosionCracking

Mechanical tensile stressescombined with chemicalsusceptibility

Micro-macro-cracks locatedat shielded or concealedareas

Initially produces scale-type indications.Ultimately leads tocracking.

The various processes of corrosion are affected by several factors. Among these are the typeof material selected for the application, the heat treatment of the material, the environment of theapplication, and the presence of any contaminants in the material itself.

ES.1.2.2 Corrosion Detection Technology AreasCorrosion detection is a subset of the larger fields of NonDestructive Evaluation (NDE) and

NonDestructive Inspection (NDI). Many of the technologies of NDE/NDI lend themselves tothe detection, characterization and quantification of corrosion damage. The following tablesummarizes the major advantages and disadvantages of the primary corrosion detection andcharacterization technologies.

Table ES-2. Summary of Corrosion Detection NDE/NDI Technologies.

Technology Advantages Disadvantages

Visual • Relatively inexpensive

• Large area coverage

• Portability

• Highly subjective

• Measurements not precise

• Limited to surface inspection

• Labor intensive

Enhanced Visual • Large area coverage

• Very fast

• Very sensitive to lap joint corrosion

• Multi-layer

• Quantification difficult

• Subjective - requires experience

• Requires surface preparation

Eddy Current • Relatively inexpensive

• Good resolution

• Low throughput

• Interpretation of output


• Multiple layer capability

• Portability

• Operator training

• Human factors (tedium)

Technology Advantages Disadvantages

Ultrasonic • Good resolution

• Can detect material loss andthickness

• Single-sided

• Requires couplant

• Cannot assess multiple layers

• Low throughput

Radiography • Best resolution (~1%)

• Image interpretation

• Expensive

• Radiation safety

• Bulky equipment

Thermography • Large area scan

• Relatively high throughput

• “Macro view” of structures

• Complex equipment

• Layered structures are a problem

• Precision of measurements

Robotics andAutomation

• Potential productivity improvements • Quality assurance

• Reliability

The study team encountered a great variety of technologies in various stages of maturity.These technologies are being pursued in university research labs, industry R&D programs andgovernment laboratories. Table ES-3 below summarizes the observed trends in the directions thatthe various technologies seem to be headed, based on the research and site visits performed in thegeneration of this sector study.

Table ES-3. Corrosion Detection Technology R&D Trends.

Technology Observed Trend

Enhanced Visual • Quantification of corrosion

• Automation of image interpretation

• Film highlighters for temporary surface modification

• Scanner-based systems

Eddy Current • More sophisticated signal and data processing (pulsed eddy current, C-scan imaging)

• More sophisticated sensors (multi-frequency)

Ultrasonic • More efficient scanning methods (dripless bubbler, gantrys, etc.)


• Dry couplants (including laser stimulation)

• Air coupled ultrasonics

Radiography • Single-sided methods (backscatter)

• Three-dimensional image processing (computed tomography)

Technology Observed Trend

Thermography • Time domain analysis (thermal wave imaging)

• Multi-spectral (dual-band infrared)


Robotics and Automation • Attached computer-controlled positioning mechanisms

• Gantrys (multi-axis)

• Crawlers (including vertical and inverted surfaces)

Data fusion • Image processing (color coding, three dimensional, etc.)

• Image correlation (C-scan, etc.)

• Multi-mode NDI

Sensor fusion • Currently only attempted within a single technology (e.g., eddy current, infrared)

• No observation of research into combining two different sensors into a single probe for simultaneous measurements

We note that it is also very important to know that corrosion does not exist. If deepcorrosion could be detected reliably and efficiently, the substantial costs associated withteardown inspections would be dramatically reduced. Maintenance plans typically call forteardown of certain structure to determine their condition. If an NDI method could accuratelydetermine the level of corrosion, including the probability that there is no corrosion present, thenthe huge costs asssociated with teardowns could be avoided. This would support the concept ofcondition based maintenance by providing an accurate assessment of the condition of the systemin question.

ES.1.3 Technology Applications

The areas where corrosion occurs, the materials in which it occurs, and the conditions underwhich it occurs all combine to make the inspection for and detection of corrosion a very difficultmatter. All defense systems experience some sort of corrosion and there are certain knownproblem areas for land, air and sea applications. The typical process of finding and identifyingcorrosion begins with visual inspection. Clearly, any damage that can be observed by visualmeans will require closer inspection. Field inspection by other means usually entails eddy currentand/or ultrasonic inspection. These types of inspections can generally be accomplished duringroutine maintenance without impacting operational availability. If additional inspection is


determined to be necessary, it is normally done by specialists under controlled conditions, suchas in a protected space or in an NDI laboratory.

ES.1.3.1 Corrosion CostsCombined, the defense establishments of the three NATIBO sponsor countries - the U.S.,

Canada, and Australia - expend on the order of $2.1 Billion per year on corrosion relatedactivities and equipment. These costs could be reduced with better NDE/NDI and corrosiondetection technology, and productivity improvements in the maintenance areas. The magnitude ofthese expenditures would make the area of corrosion detection, characterization, and prevention atempting target for future R&D.

One interesting point that was uncovered during the costs analyses is that the cost peraircraft for most types, and especially for large aircraft, has increased dramatically in the pastseven years. The general trend, as would be expected, is that as aircraft age, the relative cost ofmaintenance and repair attributable to corrosion increases significantly.

ES.1.3.2 Corrosion Detection Technologies R&D and Application ActivitiesThere are a number of different research and development activities ongoing in the field of

corrosion detection technologies. A major thrust of the research being conducted is for detectinghidden corrosion in aircraft. The military is considered the primary corrosion detectiontechnology driver. This is due in part to the fact that military systems typically are fieldedlonger, have higher cycle rates and operate in more corrosive environments than commercialsystems. And with the continual decline in defense spending, the service life for defense systemswill be extended even longer with a consequent focus on reducing maintenance costs for theseexisting systems.

As systems age, corrosion becomes one of the largest cost drivers in life cycle costs ofweapon systems. Technology has been identified as one of the primary means of reducing theimpact of corrosion on weapon systems. Throughout the military, corrosion is regarded as less asafety or technical issue but rather more of an economic issue. This is because the corrosionproblems encountered by the military in their defense systems has been detected and repairedbefore it could become a safety problem. Currently, corrosion prevention is a higher prioritywithin the military sector. The DoD S&T community is researching a number of differenttechnologies to achieve corrosion reduction in defense systems.

Within the United States, the USAF is considered to have the largest corrosion detectiontechnology development program among the three Services. The Navy has the largest monetaryinvestment in corrosion research. The Navy is also considered to have the best corrosionmaintenance and training practices. The DoD, NASA, and FAA have all established AgingAircraft Programs to address such key problems as corrosion prevention and detection.

The Canadian Department of National Defence (DND) has several different departments andlaboratories researching corrosion detection and corrosion prevention technologies. These groupsare extremely effective in coordinating their research activities. A predominant focus of theirresearch is on corrosion prevention and detection in aircraft. The AVRD/E Structures andMaterials Group oversees R&D efforts in corrosion prevention and detection.


The major Australian DoD research arm involved in studying corrosion detection technologiesis the Defence Science and Technology Office. The Office has a number of divisions addressingdifferent corrosion issues and technologies to employ to detect and correct corrosion. There is ahigh level of coordination between these divisions. The main focus of their work is on agingaircraft as well.

ES.1.3.3 Corrosion Detection Technology Industry DemographicsCorrosion detection is one small niche market of the NDE/NDT industry. NDE/NDT

equipment suppliers and service providers are not dependent upon the corrosion detectionmarket for their livelihood. In fact, the NDE/NDT end user industries run the gamut, includingdefense aerospace, commercial aerospace, automotive, shipbuilding, chemical/petrochemical,construction infrastructure, electronics/electrical, energy (utilities), ordnance, and railroad.

The industry outlook for each of these technologies varies as does the industrial basesupporting development of them. However, the NDE/NDT equipment suppliers are veryamenable to custom adapting their equipment for specific applications for a fee.

The industrial base for visual, ultrasonic, and eddy current equipment is relatively stable.

The base for film-based radiography equipment has been dealt some setbacks in recent yearsas film use is on the decline with the emergence of real-time radiography, military cutbacks, anduser concern with environmental impacts of film processing. The number of major radiographicfilm suppliers has decreased from four to three, with competition fierce among those remainingfighting for market share in an ever shrinking market.

Non-film based radiography suppliers market is in a state of flux. The market for radioscopysystems has declined due to military cutbacks. However, in response to this, suppliers havebranched out to other commercial markets such as the automotive and the electronics industriesto shore up their marketplace stance. And, with the development of portable radioscopicsystems, new uses for this technology have opened up, such as in-field inspections of pipelinesand aircraft.

The number of thermographic equipment and service providers is expanding from a handful toa larger number as the technology matures.

ES.1.4 CONCLUSIONS

ES.1.4.1 Facilitators

ES.1.4.1.1 Heightened AwarenessDue to the 1988 Aloha Airlines incident and the Military Forces’ need to extend the service

life of military systems three to four times their original design life, there is heightened awarenessto the issue of corrosion and how it is a key contributor to system failures and a driving factor interms of safety, downtime and costs. This need has been underscored by shrinking defensebudgets, reduced procurements of new equipment, and increased reliance on modifications andupgrades to current systems.


ES.1.4.1.2 Established Working GroupsThere are a number of established associations and working groups addressing the issue of

corrosion, both within North America and internationally. The U.S., Canadian and AustralianGovernments also coordinate on their research in the field of corrosion detection technologies viathe Corrosion Sub-Panel of the Technology Panel for Advanced Materials (part of ProjectReliance).

ES.1.4.1.3 New Emphasis on Cost Effectiveness/Condition Based MaintenanceAs a cost savings strategy and to eliminate the need for unnecessary maintenance, the

Services are moving away from routine maintenance where components are replaced based uponlength of time in service rather then real need. They are instituting programs where componentsare replaced based on their condition rather than to conform to a given time-in-service. This moveto condition based maintenance will provide incentives to employ newer, more efficient corrosiondetection techniques so that personnel will be better able to pinpoint the extent of their corrosionproblems and its effect on the structural integrity of the system.

ES.1.4.2 Barriers

ES.1.4.2.1 General Barriers

ES.1.4.2.1.1 Data Not Readily Available

While collecting data for this study, we discovered that recently published NDE/NDT andcorrosion detection reports are not showing up in DTIC, Dialog and other literature searches.Most of the publications that are in these databases are dated. Also, in trying to gain data fromthe depot/field level in regard to maintenance and failure analysis and the role of corrosion in theneed to repair and replace parts, it became apparent that this type of information is not easilyobtainable and, hence, is not given the visibility it needs at different levels to ensure that theserecurring corrosion problems are effectively communicated and that procedures are put in placeto rectify the situation. This was true also in the case of trying to quantify the cost of corrosionto defense systems. There is no uniform equation or standard economic model developed of theelements for determining the corrosion costs (though Warner Robins has released a 1998 reportthat breaks these elements down for aircraft). In a recent development, Tinker Air Force Base hasinitiated (late 1997) a project to establish an Aging Aircraft database.

ES.1.4.2.1.2 Research is Dispersed

There are a number of different research organizations conducting studies in the area ofcorrosion detection technologies. However, these groups are widely dispersed within DoD,DND, and the Australian DoD, reducing the visibility of the work being performed. Untilrecently, there was not a great deal of coordination in the U.S. between these different groups,especially outside of their respective Services, though more coordination has been initiatedbetween these groups as of late. The Canadian and Australian organizations are more effective incommunicating their research results within their countries; however, all three countries couldbenefit by increased coordination and sharing of findings between their research communities.And, there appears to be a disconnect between the operators and the R&D community. TheR&D community is focusing on 6.1 and 6.2 research whereas the operators are conducting


program specific research, and there does not seem to be effective communication occurringbetween the different groups.

ES.1.4.2.2 TECHNOLOGY BARRIERS

ES.1.4.2.2.1 Need for Newer Techniques Not Widely Recognized

The general impression that was formed through the numerous site visits conducted by theresearch team was that most users are satisfied with current techniques. Commercial users arewont to invest in additional corrosion detection technology that cannot be clearly justified ineconomic terms. Overall, they are satisfied that current technologies and techniques have servedto prevent catastrophic losses. They are not informed as to the potential for reduced maintenanceand repair costs that could be realized through improved corrosion detection technologies andtechniques. There is agreement that the direct and indirect costs of corrosion are substantial; thereis not agreement that these costs can be substantially reduced through further investment incorrosion detection and quantification technologies and tools. This dichotomy is best described asa “cost-benefit” question typical of the application of new technologies to existing problems.Particularly in the commercial arena, there is a sense that improved corrosion detectiontechnologies would lead to additional and, in many cases, unneeded maintenance actions.

ES.1.4.2.2.2 NDE/NDT Technologies Developed for Applications Other Than Corrosion

The first concern of structural and materials engineering has been the detection andcharacterization of defects that can be adequately modeled and therefore predicted; i.e., cracks.NDE/NDT technologies have evolved to support the science of fracture mechanics, a disciplinethat is now highly developed and quite reliable in predicting the life of complex structures inknown cyclic loading environments. These technologies, notably eddy current and ultrasonic,have proven useful for detecting and characterizing the material loss caused by corrosion.However, this is after the fact. The difficulty, and near impossibility, of predicting corrosion haspointed the work in detection technologies more toward detection of cracks than detection ofmaterial loss due to corrosion. The fact that corrosion is caused by many interacting processescontributes to this situation.

ES.1.4.2.2.3 Efficiency/Reliability of Newer Techniques and Cost/Benefits Not Well Established

The transition of a new technology from laboratory to field application is difficult. Thegovernment has been able to invest in some of the more sophisticated technologies (such asneutron radiography) that would be beyond the reach of commercial enterprises, airlines forexample. Typically, a new technology that has been developed in a laboratory is commercializedby a small company, often a start-up. Basically, the marketplace determines the success or failureof a particular technology through customer determination of the cost-effectiveness of each newoffering. Without some history that would support improved cost-effectiveness, a newtechnology or technique faces a large hurdle to implementation on a wide basis.

ES.1.4.2.2.4 Safety Concerns About Radiography Techniques

Although radiography is perhaps the most precise of the corrosion detection, and especiallycorrosion quantification, technologies, it presents the most serious hazard to the users. Indeed, in


many jurisdictions radiographic facilities and operators are required to be licensed. Fieldoperation of x-ray equipment requires that personnel be kept at some distance from the radiationsources. The emphasis on worker safety and concerns for liability judgments serve to impede thewider implementation of radiographic techniques.

ES.1.4.2.2.5 Thermography Perceived as Not Effective or Reliable

Thermography depends on operator interpretation of how an image of the structure inquestion differs from an image of a perfect or, at least, acceptable, structure. Thus, for everyimage produced, there must be a means to compare that image against that of a similar undamagedstructure. Combined with the fact that thermographic images are somewhat “fuzzy” compared toother imaging techniques (visual, radiographic, etc.), many users remain skeptical of the precisionand reliability of thermography as a corrosion detection technology. This is due to the fact thatthermographic images are captured by IR cameras that are made up of an array of detectors, eachdetector contributing one pixel to the overall picture. Thus, IR cameras have much lowerresolution than visual photographic processes (in much the same way that a photograph hasmuch better resolution than a television image).

ES.1.4.2.2.6 Human Factors Limitations

Much of the work in inspecting for corrosion is repetitive and, in a word, tedious. Take intoaccount that much of the work is done in awkward locations and sometimes under adverseenvironmental conditions (darkness, cold, etc.) Added together, the problem of inspection forcorrosion goes well beyond that of just the technology of the sensing device and the processing ofthe information. It must include an array of human factors that will limit the overall effectivenessof the inspection process.

ES.1.4.2.3 Policy/Fiscal Barriers

ES.1.4.2.3.1 Cost of Corrosion Difficult to Calculate

Determining the costs of corrosion in the life cycle of a system is difficult to calculate. Therecurrently is no baseline for this type of measurement and no good cost data at present. Hence,the costs of corrosion are not considered upfront in the acquisition cycle since no benchmark formeasuring the impact of corrosion has been established. In addition, an effective cost/benefitanalysis of the cost savings generated by implementing a corrosion detection technology isdifficult to quantify.

ES.1.4.2.3.2 Commercial Airlines/Military Have No Economic Incentive to Improve Probability ofDetecting More Corrosion

In commercial operations, there are cases where original equipment manufacturers havespecified that when corrosion is determined to be less than 10% loss per layer, the operator hasthe choice of repairing the damaged area immediately or deferring the repair until the loss reaches10%. However, the second option requires that the corroded area be re-inspected periodically.This is a heavy disincentive to the deployment of systems capable of detecting corrosion below10% if a system capable of detection of 10% is defined to be adequate. Correcting corrosiondamage at short intervals is inefficient, even though the immediate maintenance action mayprevent larger repairs later. Operators typically want to perform all corrosion repairs during a


single downtime to minimize overall downtime. This leads operators to defer corrective actionsuntil the greater 10% material loss is detected.

Perhaps the most attractive economic incentive to the commercial airlines would be improvingthe productivity of the inspection process, thereby reducing the cost of maintenance, assumingthat that can be done without compromising the safety or the service life of the aircraft.Economic incentives would surface if more developments were to occur in the area of conditionbased models where they could use the knowledge and exert control over how a corrodedcomponent is repaired and treated and tracked (such as what is presently used for fatigue andcrack growth analysis), rather than simply removing all corrosion in all cases, which can end updamaging the structure even more. In other words, corrosion models are needed to determine theconsequence of repairing it or treating it, or leaving it alone to make better informed decisions.(The models would take the effects of the corrosion damage on the fatigue life of the aircraft, andrequire accurate quantitative NDT input).

With regards to the military, employing new technologies cost money and, as with theairlines, this cost must be weighed against the return on investment to the facility. Withoutquantitative cost data to support a decision to invest in new technologies, most of the actualusers would not incur such an expense at the depot level.

ES.1.4.2.3.3 Cumbersome, Lengthy Process for Emerging Techniques to Gain WideAcceptance/FAA-OEM Approval

Currently, Service Bulletins are developed by the Original Equipment Manufacturers(OEMs) to deal with specific maintenance problems. The FAA may issue AirworthinessDirectives (ADs) to deal with problems of a more urgent nature. Service Bulletins receive FAAapproval before issuance. Airline maintenance operations may implement the Service Bulletinthrough an Alternate Means of Compliance (AMC). While the AMC is valid for the developingairline, it is not useable by another maintenance organization. In their quest to control costs,airlines seek lower cost alternatives to mandated inspection and repair requirements. Theapproval process for an AMC is lengthy and expensive. Thus, any new technology that haspromise to improve the inspection process and the productivity of the maintenance operationfaces a not inconsequential approval cycle before it is generally accepted in the customercommunity.

ES.1.4.2.3.4 Increased Training Requirements for Technicians to Use Different Technologies

Every different corrosion detection technology will entail different training requirements.Eddy current and ultrasonic sensors produce displays that require a high degree of sophisticationto properly interpret. Improved processing of newer techniques, such as stepped pulsed eddycurrent, provide c-scan images that are much more intuitive but still require expert interpretation,especially in determining when a particular threshold has been exceeded and some expensiverepair process is required. The range of technologies also expands the knowledge required tointerpret the results. Thus, for a technician to be considered fully qualified in all areas necessaryto perform a complete corrosion inspection, many more skills are required than before. Coupledwith this is the fact that the number of trained NDT inspectors is dwindling due to base closures


and consolidations and turnover at the maintenance level. Hence, the Services are experiencing aloss of corporate memory through retirement of key personnel.

ES.1.5 RECOMMENDATIONS

ES.1.5.1 Request the Corrosion Sub-Panel of TPAM Perform Added CoordinationActivities

To ensure the widespread dissemination of published reports on corrosion and thatinformation regarding corrosion detection techniques, advances, and implementation areeffectively coordinated throughout the NDE/NDI community, the Corrosion Sub-Panel ofTPAM should be approached about taking on the responsibility of:

• Coordinating and promoting interaction between the Services and identifying commonproblems

• Establishing a central repository of reports and other corrosion related information

• Improving report distribution

• Pooling information on system failures/corrosion problem areas

• Establishing a Point of Contact database of technology experts (placed online and updatedannually) so that timely consultation on specific corrosion related issues can be achieved.

If buy-in to these coordination activities is achieved, perhaps this panel could enlist the aid ofthe NTIAC to support these efforts.

ES.1.5.2 Appoint Recognized Champions to Push for Corrosion Agenda andNew/Higher Fidelity Techniques

To ensure that the entirety of system life cycle costs are considered in the procurementprocess, identify and enlist military champions to “market” the savings to Programs/ProgramManagers from 1) building into the design of the system protective measures to protect againstcorrosion and 2) including processes for detecting corrosion problems early in a system’s lifecycle. Additionally, the logistics community should be made aware of the importance ofcorrosion prevention and corrosion control in planning for the life cycle support of systems andin developing R&D requirements for extending the life cycle of weapon systems. Thesechampions could emphasize the importance of considering corrosion costs as an independentvariable for determining life cycle costs and push for establishing benchmarks for measuring theimpact of corrosion on the service life of a system. In order to better define these costs, thechampions could recommend that economic models be developed that address the costs ofcorrosion in the life cycle of the system and address the savings realized by planning forcorrosion detection upfront and detecting corrosion early on in the system’s maintenance life. Inaddition, these champions could strive to establish an integrated approach to tackling corrosionissues, ensuring that Integrated Product Teams consisting of structural engineers, NDE/NDIpersonnel and researchers address these issues in a joint fashion.


ES.1.5.3 Target Insertion/Demonstration ProgramIn order to demonstrate the benefits derived from employing a certain corrosion detection

technology(s), a widely applicable, high payoff, dual use insertion/demonstration program wouldbe an ideal mechanism. A candidate for an insertion/demonstration program might be multi-sensorand multiple data fusion, incorporating automation/robotics as deemed feasible. Thesesuggestions support the findings of the National Research Council, and have met withwidespread backing from the members of the NDE/NDI community. Industry and governmentinput would need to be solicited to develop a DoD/DND/Australian-specific program thatinvolves the fusing of as many NDE techniques as possible. Researchers, developers and end-users would participate in the identification and selection process.

ES.1.5.4 Streamline Process for Inserting Newer Techniques into OEM MaintenanceProcedures

The feedback from the research community through the OEMs back to the users andoperators of the systems should be shortened. It should be possible to incentivize this process toreward improvements that can enhance system reliability and extend the life of a system whilereducing the cost of inspection and repair. The use of electronic updates to inspection and repairmanuals can reduce the administrative delay.

ES.1.5.5 Increase Collaboration Between the Military Departments and UniversityNDE/NDT Departments on Training

Training is usually an afterthought following the development of new inspection technologiesand tools. It should be possible to procure integrated training along with any new inspectiontools. Such training would be essential until each using organization was able to develop a core ofexpertise and thereby be able to conduct their own training programs.


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Table of Contents

EXECUTIVE SUMMARY ........................................................................................................ES-1

1. INTRODUCTION ..................................................................................................................... 1

1.1 BACKGROUND........................................................................................................................... 11.2 PURPOSE .................................................................................................................................. 21.3 OBJECTIVES .............................................................................................................................. 31.4 SCOPE...................................................................................................................................... 31.5 METHODOLOGIES ...................................................................................................................... 41.6 REPORT STRUCTURE................................................................................................................... 5

2. CORROSION TECHNOLOGY.................................................................................................. 6

2.1 CORROSION FUNDAMENTALS....................................................................................................... 62.1.1 Definition of Corrosion ........................................................................................................ 72.1.2 Types of Corrosion.............................................................................................................. 7

2.1.2.1 General Corrosion or Uniform Attack.............................................................................................................................82.1.2.2 Pitting......................................................................................................................................................................................82.1.2.3 Intergranular and Exfoliation Corrosion........................................................................................................................82.1.2.4 Crevice Corrosion.................................................................................................................................................................92.1.2.5 Filiform Corrosion ................................................................................................................................................................92.1.2.6 Galvanic (Dissimilar Metal) Corrosion..........................................................................................................................92.1.2.7 Environmental Embrittlement and Stress Corrosion Cracking..............................................................................102.1.2.8 Corrosion Fatigue...............................................................................................................................................................102.1.2.9 Combined Mechanisms......................................................................................................................................................112.1.2.10 Summary ..............................................................................................................................................................................11

2.1.3 Factors Affecting Corrosion ............................................................................................... 122.1.3.1 Effect of Material Selection...............................................................................................................................................122.1.3.2 Effect of Heat Treatment .....................................................................................................................................................132.1.3.3 Effect of Environment.........................................................................................................................................................132.1.3.4 Effect of Contamination.....................................................................................................................................................13

2.2 CORROSION DETECTION TECHNOLOGY AREAS .............................................................................. 132.2.1 Visual ............................................................................................................................. 13

2.2.1.1 Techniques and Technologies.........................................................................................................................................142.2.1.2 Advantages and Disadvantages .....................................................................................................................................142.2.1.3 Current Research .................................................................................................................................................................15

2.2.2 Eddy Current ................................................................................................................... 162.2.2.1 Techniques and Technologies.........................................................................................................................................162.2.2.2 Advantages and Disadvantages .....................................................................................................................................172.2.2.3 Current Research .................................................................................................................................................................18

2.2.3 Ultrasonic ....................................................................................................................... 182.2.3.1 Techniques and Technologies.........................................................................................................................................192.2.3.2 Advantages and Disadvantages .....................................................................................................................................202.2.3.3 Current Research .................................................................................................................................................................20

2.2.4 Radiography .................................................................................................................... 212.2.4.1 Techniques and Technologies.........................................................................................................................................212.2.4.2 Advantages and Disadvantages .....................................................................................................................................212.2.4.3 Current Research .................................................................................................................................................................22

2.2.5 Thermography.................................................................................................................. 222.2.5.1 Current Research .................................................................................................................................................................232.2.5.2 Advantages and Disadvantages .....................................................................................................................................23

2.2.6 Other Technologies ........................................................................................................... 242.3 SUMMARY.............................................................................................................................. 25

3. TECHNOLOGY APPLICATIONS........................................................................................... 27

3.1 AIR APPLICATIONS ................................................................................................................... 293.2 SEA APPLICATIONS................................................................................................................... 293.3 LAND APPLICATIONS ................................................................................................................ 293.4 SUMMARY.............................................................................................................................. 30

4. CORROSION COSTS............................................................................................................. 30


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4.1 DEFENSE ................................................................................................................................ 314.1.1 U.S. Defense .................................................................................................................... 314.1.2 Canadian Defense Costs .................................................................................................... 344.1.3 Australian Defense Costs ................................................................................................... 344.1.4 Summary ......................................................................................................................... 35

4.2 COMMERCIAL.......................................................................................................................... 354.3 SUMMARY.............................................................................................................................. 36

5. CORROSION DETECTION TECHNOLOGIES RESEARCH AND APPLICATION ACTIVITIES........................................................................................................................................................ 37

5.1 INTRODUCTION........................................................................................................................ 375.2 DEFENSE SPONSORED ACTIVITIES................................................................................................ 37

5.2.1 U.S. Activities .................................................................................................................. 375.2.1.1 U.S. Air Force.......................................................................................................................................................................37

5.2.1.1.1 Air Force Office of Scientific Research.................................................................................................................395.2.1.1.2 USAF Wright Laboratory Materials Directorate, Wright-Patterson AFB...............................................405.2.1.1.3 U.S. Air Force Corrosion Program Office, Warner Robins AFB...................................................................455.2.1.1.4 Aging Aircraft Office ................................................................................................................................................465.2.1.1.5 Sacramento Air Logistics Center, McClellan AFB ..........................................................................................475.2.1.1.6 Oklahoma City Air Logistics Center, Tinker AFB..........................................................................................48

5.2.1.2 U.S. Navy ..............................................................................................................................................................................495.2.1.2.1 Office of Naval Research ..........................................................................................................................................505.2.1.2.2 Naval Research Laboratory ....................................................................................................................................505.2.1.2.3 Carderock Division, Naval Surface Warfare Center (CDNSWC) - Philadelphia.....................................505.2.1.2.4 Naval Surface Warfare Center, Carderock Division – Bethesda...................................................................535.2.1.2.5 Naval Air Systems Command (NAVAIR) ...........................................................................................................545.2.1.2.6 US Navy Mid-Atlantic Regional Maintenance Facility, Norfolk, VA.......................................................555.2.1.2.7 Jacksonville Naval Aviation Depot ....................................................................................................................565.2.1.2.8 North Island, NAVAIR............................................................................................................................................575.2.1.2.9 Pearl Harbor Naval Shipyard (PHNSY), Pearl Harbor, HI ...........................................................................57

5.2.1.3 U.S. Army..............................................................................................................................................................................595.2.1.3.1 U.S. Army Research Laboratory (ARL), Metals Research Branch...............................................................595.2.1.3.2 Army Research Laboratory (ARL), Vehicle Technology Center..................................................................605.2.1.3.3 Army Aviation Missile Command, Depot Maintenance Engineering Team.............................................605.2.1.3.4 U.S. Army Pacific, Ft. Shafter, HI...........................................................................................................................61

5.2.2 Marine Corps................................................................................................................... 635.2.3 Canadian DND Activities................................................................................................... 65

5.2.3.1 Air Vehicle Research Detachment ..................................................................................................................................655.2.3.2 Institute for Aeropsace Research (IAR), National Research Council Canada....................................................665.2.3.3 Quality Engineering Test Establishment (QETE)....................................................................................................675.2.3.4 Aerospace and Telecommunications Engineering Support Squadron (ATESS)..............................................68

5.2.4 Australian DoD Activities................................................................................................... 685.2.4.1 Defence Science and Technology Office (DSTO) .......................................................................................................695.2.4.2 RAAF Richmond.................................................................................................................................................................745.2.4.3 Tactical Fighter Logistics Management (TFLM) Squadron, RAAF Williamtown...........................................755.2.4.4 RAAF Amberley, Queensland.........................................................................................................................................77

5.3 DEPARTMENT OF TRANSPORTATION............................................................................................. 805.3.1 FAA Technical Center........................................................................................................ 805.3.2 FAA Airworthiness Assurance NDI Validation Center (AANC) ................................................. 845.3.3 U.S. Coast Guard............................................................................................................. 86

5.4 NASA SPONSORED ACTIVITIES .................................................................................................. 875.4.1 NASA Langley Research Center ........................................................................................... 875.4.2 Jet Propulsion Laboratory.................................................................................................. 885.4.3 NASA Kennedy Space Center............................................................................................... 89

5.5 DEPARTMENT OF ENERGY (DOE)................................................................................................. 905.5.1 Lawrence Livermore National Laboratory............................................................................. 905.5.2 Lawrence Berkeley National Laboratory ............................................................................... 92

5.6 DEPARTMENT OF COMMERCE/NIST............................................................................................. 935.7 COMMERCIALLY SPONSORED ACTIVITIES ..................................................................................... 93

5.7.1 ARINC............................................................................................................................ 935.7.2 Boeing Information, Space and Defense Systems, Phantom Works, Seattle Materials


ix

and Processes (M&P) NDE Group ..................................................................................... 945.7.3 C. W. Pope & Associates Pty. Ltd.......................................................................................... 975.7.4 Diffracto Limited.............................................................................................................. 985.7.5 Engineering Testing and Research Services (ETRS)................................................................1005.7.6 McDonnell Douglas Corporation (Now a wholly owned susidiary of The Boeing Company).........1015.7.7 PRI Instrumentation, Inc. ..................................................................................................1025.7.8 Southwest Research Institute ..............................................................................................1035.7.9 Thermal Wave Imaging, Inc. ..............................................................................................1045.7.10 Tektrend International.....................................................................................................1055.7.11 TPL, Inc. ......................................................................................................................1065.7.12 Utex Scientific Instruments...............................................................................................106

5.8 COMMERCIAL AIRLINE ACTIVITIES.............................................................................................1075.8.1 Aloha Airlines .................................................................................................................1075.8.2 Air Canada - Dorval ........................................................................................................1075.8.3 Northwest Airlines, Minneapolis, Minnesota ........................................................................1085.8.4 Qantas Airways...............................................................................................................109

5.9 UNIVERSITY/ACADEMIC RESEARCH ACTIVITIES............................................................................1115.9.1 Carnegie Mellon Research Institute.....................................................................................1115.9.2 College of William and Mary, Department of Applied Science..................................................1115.9.3 Iowa Sate University, Center for Nondestructive Evaluation....................................................1115.9.4 Johns Hopkins Laboratory.................................................................................................1125.9.5 Royal Military College......................................................................................................1135.9.6 UCLA............................................................................................................................1135.9.7 University of Dayton Research Institute................................................................................1145.9.8 University of Pennsylvania.................................................................................................1155.9.9 University of Washington ..................................................................................................1155.9.10 Wayne State University ....................................................................................................115

5.10 SUMMARY ...........................................................................................................................116

6. CORROSION DETECTION TECHNOLOGIES INDUSTRY DEMOGRAPHICS.......................116

6.1 VISUAL.................................................................................................................................1166.1.1 Equipment Providers ........................................................................................................1176.1.2 Industry Outlook ..............................................................................................................118

6.2 EDDY CURRENT......................................................................................................................1196.2.1 Equipment Suppliers.........................................................................................................1196.2.2 Industry Outlook ..............................................................................................................1196.2.3 Ultrasonics .....................................................................................................................120

6.2.3.1 Equipment Providers......................................................................................................................................................1206.2.3.2 Industry Outlook.............................................................................................................................................................121

6.2.4 Radiography ...................................................................................................................1226.2.4.1 Equipment Providers......................................................................................................................................................1226.2.4.2 Industry Outlook.............................................................................................................................................................122

6.2.5 Thermography.................................................................................................................1246.2.5.1 Equipment Suppliers ......................................................................................................................................................1246.2.5.2 Industry Outlook.............................................................................................................................................................124

6.3 SUMMARY.............................................................................................................................125

7. CONCLUSIONS REGARDING FACILITATORS ENABLING MORE WIDESPREAD USE OF CORROSION DETECTION TECHNOLOGIES ........................................................125

7.1 HEIGHTENED AWARENESS........................................................................................................1257.2 ESTABLISHED WORKING GROUPS...............................................................................................1267.3 NEW EMPHASIS ON COST EFFECTIVENESS/CONDITION BASED MAINTENANCE ....................................126

8. CONCLUSIONS REGARDING BARRIERS AFFECTING THE WIDESPREAD ADOPTION OF CORROSION DETECTION TECHNOLOGIES............................................126

8.1 GENERAL BARRIERS ................................................................................................................1268.1.1 Data Not Readily Available ...............................................................................................1278.1.2 Research Is Dispersed.......................................................................................................127

8.2 TECHNOLOGY BARRIERS..........................................................................................................127


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8.2.1 Need for Newer Techniques Not Widely Recognized ...............................................................1278.2.2 NDE/NDT Technologies Developed for Applications Other Than Corrosion ..............................1288.2 .3 Ef ficie ncy/R eliab ility of N ewer Techn iques and Cost/ Benef its N ot We ll Es tabli shed...............1288.2 .4 Sa fety Conce rns A bout Radio graph y Tec hniqu es ................................................................1288.2 .5 Th ermog raphy Perc eived as N ot Ef fecti ve or Reli able .........................................................1298.2 .6 Hu man F actor s Lim itati ons .............................................................................................129

8.3 POLICY/FISCAL BARRIERS ........................................................................................................1298.3.1 Cost of Corrosion Difficult to Calculate..............................................................................1298.3.2 Commercial Airlines/Military Have No Economic Incentive to Improve Probability of Detecting More Corrosion................................................................................................1298.3.3 Cumbersome, Lengthy Process for Emerging Techniques to Gain Wide Acceptance/ FAA-OEM Approval .........................................................................................................1308.3.4 Increased Training Requirements for Technicians to Use Different Technologies.........................130

9. RECOMMENDATIONS OF THE NATIONAL RESEARCH COUNCIL....................................130

10. RECOMMENDATIONS........................................................................................................131

10.1 REQUEST THE CORROSION SUB-PANEL OF TPAM PERFORM ADDED COORDINATION ACTIVITIES.........13210.2 APPOINT RECOGNIZED CHAMPIONS TO PUSH FOR CORROSION AGENDA AND NEW/HIGHER FIDELITY TECHNIQUES..........................................................................................................13210.3 TARGET INSERTION/DEMONSTRATION PROGRAM ........................................................................13310.4 STREAMLINE PROCESS FOR INSERTING NEWER TECHNIQUES INTO OEM MAINTENANCE PROCEDURES.......................................................................................................................13310.5 INCREASE COLLABORATION BETWEEN THE MILITARY DEPARTMENTS AND UNIVERSITY NDE/NDT DEPARTMENTS ON TRAINING...................................................................................124

APPENDIX A ............................................................................................................................A-1

APPENDIX B ............................................................................................................................B-1

APPENDIC C ............................................................................................................................C-1


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List of Figures

FIGURE 1-1. TECHNOLOGY ADVANCEMENTS................................................................................... 3FIGURE 1-2. CORROSION DETECTION TECHNOLOGY APPLICATION ................................................ 4FIGURE 1-3. STUDY METHODOLOGY ................................................................................................ 4

List of TablesTABLE 2-1. CORROSION TYPES AND CHARACTERISTICS.............................................................. 12TABLE 2-2. SUMMARY OF CORROSION DETECTION NDE/NDI TECHNOLOGIES.............................. 24TABLE 2-3. CORROSION DETECTION TECHNOLOGY R&D TRENDS................................................ 25TABLE 4-1. U.S. AIR FORCE TOTAL COSTS - FY97 ........................................................................... 32TABLE 4-2. EXAMPLE U.S. AIR FORCE COSTS BY WEAPON SYSTEM............................................ 33TABLE 4-3. CHANGES IN COST PER AIRCRAFT, 1990-1997.............................................................. 33TABLE 4-4. TOTAL CORROSION COSTS, U.S. ARMY 800-SERIES TRUCKS ..................................... 35TABLE 5-1. THE AGING CANADIAN FORCES AIR FLEET................................................................. 60TABLE 5-2. CURRENT BOEING DEFENSE AND SPACE GROUP R&D AGING AIRCRAFT CONTRACTS........................................................................................... 88TABLE 5-3. MCDONNELL DOUGLAS CORROSION DETECTION R&D FUNDING PROFILE................. 93TABLE 5-4. SOME USERS OF UTEX PULSER RECEIVERS................................................................ 99TABLE 9-1. CRITICAL CORROSION NDE INSPECTION NEEDS FOR AGING AIRCRAFT ...................122


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1

1. INTRODUCTION

1.1Background

The North American Technology andIndustrial Base Organization (NATIBO) ischartered to facilitate cooperative technologyand industrial base planning and programdevelopment among the U.S. militaryServices and Canada. To further thismission, the NATIBO has spearheaded aneffort to address the challenges of advancingand maintaining technological superiority inlight of reduced government research anddevelopment funding. The criteria used forselecting technologies to study through thisprogram are:

• The candidate is a key technology area ofhigh interest

• There is potential for both military andcommercial applications

• Development and/or production exists inboth the U.S. and Canada

• There is a good window of opportunityfor investment and application.

Through this initiative, common areas ofinterest are assessed jointly, allowingparticipating organizations to capture theinformation they need cost effectively, avoidduplication of effort, and capitalize on scarceresources.

Through a lengthy selection process, thearea of corrosion detection technologies waschosen as the technology area to addressthrough the NATIBO’s technology baseenhancement program. Joining the NATIBOin this effort for the first time is theAustralian Department of Defence. In thecourse of high level, trilateral discussions,

the Australian Government determined thatthis technology area of study was of keeninterest to them as well and decided tobecome involved in this NATIBO study.

Corrosion involves a number of issueswhich need to be taken under considerationwhen addressing the seriousness of thecorrosion problem throughout the U.S.Department of Defense, the CanadianDepartment of National Defence, and theAustralian Department of Defence.Corrosion is a force structure issue. Everyyear, some number of weapons systems(aircraft, vehicles, etc.) are retired based onbeing too expensive to repair. These assetsare not replaced on a one-for-one basis, thusthe overall force structure is reduced, for anet result of a loss of capability. As systemsage, their associated maintenance and repairneeds increase. For example, the depotoverhaul time for KC-135 aircraft has nearlydoubled in recent years. This means thateach asset will be out of the active (combatcoded) fleet for longer periods, reducing thenumber of assets available for operations atany given time.

Corrosion is an economic issue. It coststhe three Governments millions of dollarsper year to manage corrosion. Corrosion is,in many instances, difficult to detect anddifficult to repair. The expected service lifeof an older system is harder to predict whencorrosion damage has been incurred.Increased expenses for inspection,maintenance and repair inevitably meanfewer resources available for operations,training and contingencies. Furthermore,some of the most accurate methods fordetection and characterization of corrosionare also very expensive.


2

Corrosion is a technical issue. The causesand effect of corrosion are not wellunderstood. There are many forms andcombinations of corrosion just as there aremany different means to detect andcharacterize corrosion. No single means ofdetection is either ideal or even suitable forall forms of corrosion. As in so many otherareas, the area of corrosion detection islimited by a probability of detection and bythe characterization and accuracy of theresults. Thus corrosion is a highly complextechnical issue. Even so, it is often treated asa subset of nondestructive testing andevaluation.

Corrosion is a long-term issue. Newersystems are designed and built using bettermaterials, adhesives, coatings, etc. Theyincorporate many of the lessons learnedfrom building, operating and maintainingolder systems. The corrosion problemoccurs slowly and is obviously mostadvanced in older systems. The maintenancerequirements of older systems increase withthe age of the system, though this increase isnot entirely predictable.

Corrosion is an education and trainingissue. Corrosion involves many differentdisciplines, including mechanics, strength ofmaterials, electrical engineering, chemistry,and others. Corrosion is often treated as atechnician-level problem in the field. Whilethis is not a glamorous career field, ittypically takes on the order of ten yearsexperience to become considered highlyqualified in the field. The typical corrosioninspector, if he does his job well, will likelygenerate only bad news, i.e., the need formore than planned maintenance and repair,and therefore higher than planned expenses.The education and training of corrosioninspectors tends to be ad hoc rather than

defined by specific curricula and careerprogression ladders.

Corrosion is a safety issue. This study isnot intended to exhaustively examine thesafety impact of corrosion, but it cannot beignored. Within previous case studies, thereis evidence to suggest that corrosion is aprimary cause factor and a contributingcause factor in a substantial number ofsafety incidents and accidents.

In addition to these considerations, theDoD, DND, and Australian corrosiontechnology infrastructure is being affectedby a number of factors that are having animpact on resources to combat corrosion andextend the life of existing systems. Theseinclude:

• Possible reduction of current budget levels

• Loss of manpower through baseclosures and consolidations

• Loss of corporate memory through retirement of key personnel

• Turnover at the maintenance level

• Increased environmental restrictions.

1.2Purpose

The purpose of this study is to assessthe industrial base, maturity, level of use,utility, and viability of corrosion detectiontechnologies for land, air and seaapplications. Non-destructiveevaluation/non-destructive inspection(NDE/NDI) equipment manufacturers havenot been focused on developing corrosiondetection technologies for military systems.Rather, they have concentrated ondeveloping technologies to detect cracks inpipes in the electric, nuclear power and


3

pipeline industries because these industriesoffer a higher payoff.

This report investigates corrosiondetection technologies from technological,policy, financial, cultural, and effectivenesspoints of view and develops conclusionsregarding the status of these technologiesfrom each of these perspectives.Recommendations are presented regardingactions that the defense and industrialcommunity might consider in response tothese conclusions.

1.3Objectives

This study identifies and assesses thematurity and applicability of corrosiondetection technologies to solve the problemof detecting corrosion that is found in boththe defense and commercial industry.

The objectives of this study are to:

• Conduct a complete and thoroughanalysis of present and emergingcorrosion detection technologies

• Identify land, sea, and airapplications of corrosion detectiontechnologies

• Identify corrosion detectionproponents, equipment developers andresearchers in government, industry andacademia

• Identify barriers and impedimentsblocking the expansion of corrosiondetection technologies into the industrialbase

• Develop recommendations forgovernment and/or industry action toeliminate barriers and address issues.

This report explores the military andcommercial applications of these technologies

and the transfer of the technologies amonggovernment organizations and betweengovernment and private industry. Advantagesand limitations of these technologies arediscussed and compared. From this analysis,conclusions regarding these technologies andtheir further commercialization are discussed.The recommendations addressing theseconclusions are then provided for potentialfuture action.

1.4Scope

This study encompasses the collectionand analysis of technical, business, andpolicy information related to corrosiondetection technology research efforts andindustrial capabilities in the U.S., Canadaand Australia. The corrosion detectiontechnologies investigated and analyzed inthis report are:

• Visual - used for quick inspection ofwelds and components; can be used withtelevision camera systems and enhancedby using low power magnifying glasses

• Enhanced Visual - optical inspectionusing CCD cameras, special optical andillumination systems and sometimesscanners. Can generate digital output foruse with other systems.

• Radiography - technique using x-rays, neutrons, or gamma rays to imagematerial flaws on film or magnetic media

• Ultrasonics- technology that usessound waves to detect flaws or measurematerial thickness

• Eddy current - an electromagnetictechnique used on conductive materials

• Thermography - infrared imaging toidentify abnormal thermal characteristics.


4

Within each of these technology areas,emerging technological advances are explored(see Figure 1-1 below).

Visual

Radiography

Ultrasonics

Eddy Current

Thermography

980090-01

Figure 1-1. Technology Advancements.

Other technologies that are addressedinclude liquid penetrant, microwave NDE,acoustic emission, electrochemical sensors,embedded fiber-optic sensors, laser speckleand laser moiré, galvanic thin film sensors,neural net and classifier development, andelectrochemical impedance spectroscopy(EIS).

Though these technologies are used in awide range of applications throughout thecourse of manufacturing, this study isfocused on NDI as it relates to corrosion

detection of systems that are inservice (see Figure 1-2 above).

1.5Methodologies

The corrosion detectiontechnology study required aclear, concise, and well-definedmethodology to surveygovernment, industry andacademia effectively andcompile military, commercial,political, marketplace andacademic perspectives. Thedata collected and analyzed for

this study were drawn from previouslypublished reports, conference proceedings,journal articles, Internet home pages andother online sources, as well as from

Processing

In-Service

Materials Characterization

Process Sensing

Non-Destructive InspectionDuring Manufacture

Non-Destructive InspectionIncludingCorrosion Detection

980090-02

Figure 1-2. Corrosion Detection TechnologyApplication.


5

discussions with U.S., Canadian andAustralian representatives from industry,government and academia. Themethodology employed is depicted inFigure 1-3.

The study group’s goal was to meet with arepresentative sample of corrosion detectiontechnology researchers, equipment providers,end users, proponents and policy makers.Factors taken into consideration in selectingsites to visit included volume and businesswith the individual Services and with industry,industrial sector involved, market niche, stateof the technology, applications, and newtechnology development. Site visits wereconducted in six regional areas: U.S. WestCoast, U.S. Midwest, U.S. Southwest, U.S.Northeast, Canada, and Australia.

Whe n it was d eterm ined that anind ustry , uni versi ty, o r gov ernme nt si tewou ld no t be visit ed, a n ext ensiv e pho neint ervie w was cond ucted . Dat a col lecti ongui delin es we re de velop ed an d use d tofac ilita te ob taini ng da ta fr om al l poi nts o fcon tact eithe r thr ough telep honeint ervie ws an d/or site visit s.

DataCollection

TechnologyAssessment

Research

Facilitators

Barriers

IndustrialBase

CostAnalysis

Findings

980090-03

LiteratureSearch

SiteVisits

PhoneInterviews

Fig ure 1 -3. S tudy Metho dolog y.

Data collected from relevant documents,World Wide Web sites, site visits, and phone

interviews were analyzed and incorporatedinto key sections of this report: technologyoverview, applications, corrosion costs,research activities, industry demographics,facilitators, barriers, and recommendations.This report functioned as a working documentthroughout the data collection and analysisphases of this study.

1.6Report Structure

Section 2 of this report discusses thefundamentals of corrosion, defines thedifferent types of corrosion, and factorsaffecting corrosion. It describes the differenttechnologies, the types of techniquesemployed in the technology area, and theadvantages and disadvantages of thetechnologies.

Section 3 provides an overview ofcurrent and potential applications ofcorrosion detection technologies. Bothmilitary and commercial land, air and seaapplications are considered.

Section 4 addresses the issue ofcorrosion costs and demonstrates howcorrosion is an increasingly expensiveproblem.

Section 5 presents an overview of thegovernment, commercial and academicinstitutions currently active in the corrosiondetection technologies field.

Section 6 highlights the industrydemographics of the corrosion detectiontechnologies arena, and projects the industryoutlook for each technology.

Section 7 addresses facilitators enablingadvancement of current and emergingcorrosion detection technologies.


6

Section 8 then addresses barriersaffecting the widespread adoption of thesetechnologies.

Section 9 provides relevantrecommendations made by the NationalResearch Council in a related study.

Section 10 provides specificrecommendations for capitalizing on thefacilitators and addressing the barriersdiscussed in the report.

Helpful appendices are also provided toassist in the reading of the report.

2. Corrosion Technology

This section provides an overview of thephysical phenomena of corrosion, adescription of its various forms andcomplexities, and an overview of theprominent technologies employed and underdevelopment to detect and characterizecorrosion.

2.1Corrosion Fundamentals

Corrosion is a physical phenomenon thatresults in the loss of structural material andthe generation of the products of corrosion,i.e., scale and metallic salts. The presence ofthe products of corrosion are one of thesymptoms of the process. The result is thereduction of structural strength and thereforethe useful life of a system. In general,corrosion is time related whereas fatigue andcrack growth are cycle related. However,both produce the same result, a loss ofphysical strength of the structure of thesystem in question.

Both structural fatigue and corrosion giverise to the entire Non Destructive Evaluationand Inspection (NDE/NDI) industry. Thisindustry and its research activities in

industry, academia and government focus ontechnologies that are useful for detection ofstructural flaws in the form of cracks andcorrosion, both of which reduce the inherentstrength of the structure.

Over the past 30 years or so, greatprogress has been made in the modeling andunderstanding of crack growth. This isexhibited in the relatively new field of scienceknown as fracture mechanics. It is nowpossible to predict with high accuracy andassurance the growth of cracks in variousstructural materials. This science is now thebasis for calculating the useful life ofsystems, such as aircraft, exposed to apredictable stress history.

Similar progress in the modeling andunderstanding of corrosion has not beenmade. This is at least partially due to themany forms and combinations of corrosion,each with different outcomes. Prediction ofcorrosion damage now relies heavily onperiodic inspection, often requiringdisassembly of the structure to find andmeasure the effects of the many forms ofcorrosion.

Research in NDE/NDI for corrosion isnow being conducted by many organizationsfor many different applications. Research isbeing sponsored under programs such as theFAA’s Aging Aircraft program. Much of thebasic research is still at the academic stagewith few transitions to commercialapplication. Most researchers agree that thereis no single “silver bullet” that will enableaffordable, large improvements in corrosionrelated NDE/NDI technology in the nearterm.

Corrosion itself is insidious. It occursmore or less continuously and tends to seekout areas that are not amenable to inspection,


7

washing or periodic re-coating. It occurs inareas that are hidden from direct view and inareas that are difficult to predict. It isfrequently masked by structural features.

Corrosion of primary structure, the loadbearing structure subject to the higheststresses and therefore accelerated stresscorrosion, can be masked by secondarystructure. For example, corrosion in anaircraft’s wing spar can be hidden by skin,fillets and fuel tanks that cover the affectedarea of the spar. Furthermore, repair ofcorrosion in many cases tends to hasten itsrecurrence and its subsequent rate ofpropagation. Finally, because corrosion is amulti-disciplinary phenomenon and itsdetermination is only part science andsomewhat subjective, the education andtraining of corrosion specialists is a particularchallenge.

2.1.1 Definition of CorrosionCorrosion is typically defined as the

degradation of a material, usually a metal,because of a reaction with its environment.The reactions by which corrosion damageoccurs are varied, but can be generallyclassified as electrochemical, chemical, orphysical. Corrosion is especially importantbecause of its insidious nature, occurringwithin materials and structures in places andtimeframes that are difficult to predict andlocate. Corrosion is the destruction of metalsby chemicals or electrochemical action and iscaused by a chemical reaction between metals(serving as electrodes) and an aqueoussolution containing different ions and/ordissolved oxygen, acting as the electrolyte.Corrosion is to be distinguished from erosion,which is primarily destruction by mechanicalaction, such as occurs in high pressure, highflow rate tubing.

2.1.2 Types of CorrosionDegradation of material properties by

corrosion, or corrosion damage, can takemany forms. There have been several


8

different organizations of this information,each useful from a particular viewpoint.

For exam ple, the m echan isms of co rrosi oncan be d ivide d int o tim e dep enden t, ti merel ated, and time indep enden t cat egori es.Oth er ca tegor izati ons a re us eful. For thepur poses of t his r eport , we shall cons iderthe type s of corro sion listed and describedin the following sections. The wide varietyof forms of corrosion gives emphasis to thedifficulty of detecting all forms with equalassurance and accuracy. In general, detectionof corrosion is concerned with measuring theamount of material lost through thecorrosion process. Such material loss is anindication of the residual strength of thematerial and therefore the remaining usefullife of the structure in question.

The following descriptions of the variousforms and types of corrosion and corrosiveprocesses are those generally used by J. J.DeLuccia, Ph.D., former Senior MaterialsEngineer with the Naval Air DevelopmentCenter and now a Professor at theUniversity of Pennsylvania, as described inAIAA paper 91-0953.

2.1.2.1 General Corrosion orUniform Attack

As its name implies, general corrosionattack causes the metal to be consumeduniformly over the entire surface that iswetted within the corrosive environment.When a metal experiences general corrosion,the anodes and cathodes on the surfacecontinually switch their behavior(polarization) so that a relatively uniformconsumption of the metal surface occurs withtime. This type of corrosion is most easilytreated, but it is not a particularly criticalproblem on aircraft where localized corrosionis a greater problem. General corrosion attackwould be of greater concern where large areas

are exposed without surface treatments orperiodic cleaning. This occurs, for instance,on ships and trucks which have large surfaceareas vulnerable to surface damage andsubsequent corrosion.

2.1.2.2 PittingPitting is a form of corrosion that occurs

locally and thus results in consumption ofmetal in a non-uniform fashion at a specificlocation. This localized attack, pitting, is moreinsidious and hence more dangerous thangeneral corrosion. Unfortunately, most of thecommon metals used in defense systemconstruction are susceptible to this type ofcorrosion. Aluminum alloys and stainlesssteels are prime examples of metals that willpit in the presence of certain reducing anions.The ubiquitous chloride ion falls into thiscategory. The hydrolysis reaction that occursin a pit produces a metal hydroxide andhydrochloric acid. The hydrochloric acidperpetuates the process, making pittingcorrosion a difficult form to counter.

Pitting corrosion is common on aircraft,ship and land vehicle structures since agehardenable, high strength aluminum alloys andsteels are particularly susceptible to this typeof attack. The localized corrosion of pitting isitself deleterious. Additionally, the negativegeometrical aspect of pits, acting as notches orcracks, can trigger more damage when stressesare superimposed on the part. Thisphenomenon will be further described inSections 2.1.2.7 and 2.1.2.8.

2.1.2.3 Intergranular andExfoliation Corrosion

All solid metals are crystalline in nature.All metallic structures therefore consist of amultitude of tiny crystals called grains.When corrosion occurs preferentially alongthe boundaries of these grains, the metal issaid to experience intergranular corrosion. A


9

large percentage of all aircraft structuresconsist of aluminum alloys that have beenworked (rolled or pressed during forming)and hence exhibit an elongated grain

structure. When intergranular corrosionoccurs in an elongated grain structure, it iscalled exfoliation. The buildup ofintergranular corrosion products along theelongated grains is exhibited as bulging orexpansion of the material, caused by abuildup of the corrosion products within thematerial. This type of corrosion typicallystarts at a machined surface (such as afastener hole) where the machining processexposes and slightly opens the inter-grainboundaries. Thus, this type of corrosion istypically discovered as a bulging or“pillowing” around rivets and fasteners usedin aircraft, ships and land vehicles.

2.1.2.4 Crevice CorrosionIf a sta gnant area in t he fo rm of a

cre vice or de bris depos it oc curs on th esur face of a metal expo sed t o an aqueo usenv ironm ent, accel erate d cor rosio n can beexp ected to o ccur withi n the crev ice o rdeb ris d eposi t. Th e are a wit hin t he cr evice or under the depos it be comes a to tal a node(th e ele ctrod e whe re ac tive corro sionocc urs). The areas imme diate ly ad jacen t tothe crev ice o r deb ris b ecome the opera tivecat hode. A cl assic exam ple o f cre vicecor rosio n is that which occu rs at lap joint stha t all ow in gress of t he en viron ment. Muc h of the c revic e cor rosio n obs erved onair craft is a resu lt of diff erenc es in oxyg encon centr ation with in th e cre vice andadj acent to i t. Cr evice corr osion as w ell a sthe prev iousl y def ined pitti ng is furt herexa cerba ted b y the stag nant corro sivepro ducts beco ming more acidi c wit h tim e.The same hydr olysi s rea ction desc ribed ear lier occur s wit hin a crev ice.

It should be noted that bonded aircraftjoints can experience bond material (usuallyepoxies) deterioration. When these bondingresins deteriorate, they become brittle andsubject to moisture accumulation. Thus thepresence of a deteriorated surface bond can actto retain moisture and lead to crevice corrosionof the joint. Even in the absence of resinbonding, fastened joints can experience crevicecorrosion at the interface of the joinedsurfaces. This form of crevice corrosion canalso cause surface bulging or “pillowing.”

2.1.2.5 Filiform CorrosionFiliform corrosion occurs under paint

films in hot and humid environments. It maystart as a corrosion pit at a paint defect or atan unpainted edge. Instead of the pitprogressing deeply into the metal, it remainsclose to the surface and meanders aboutunder the paint film or even under thecladding of some clad aluminum alloys. Thisform of corrosion is more prevalent inaircraft, vessels, and land vehicles operatedin hot, wet conditions. The appearance offiliform corrosion, once the paint or surfacefilm is removed, gives the visual impressionof surface worm damage as sometimesoccurs in wood products.

2.1.2.6 Galvanic (DissimilarMetal) Corrosion

If two different metals are brought intocontact in an electrolytic solution, the resultingsystem is the familiar galvanic cell. The metalnearer the top of the galvanic series (orgalvanic scale) forms the anode; the othermetal is the cathode. The electrical connectionneeded to complete the circuit is provided bythe contact between the two metals. The rateof corrosion activity is governed by therelative positions of the metals in the galvanicseries, the more widely separated metals


10

corroding faster due to the greater difference inelectrical potential between them.

As in al l ele ctroc hemic al co rrosi onpro cesse s, da mage is ob serve d as metal los s at the a node, acco mpani ed by thefor matio n of corro sion- produ ct de posit son one o r bot h sur faces . The rate ofcor rosio n wil l be a fun ction of t he ga lvani cdif feren tial or se parat ion o n the galv anicsca le. A s an examp le, b oats desig ned f orope ratio n in seawa ter t ypica lly e mploy sac rific ial a nodes (usu ally zinc, near thebot tom o f the galv anic serie s) to int entio nally draw the corro sion proce ssawa y fro m cri tical comp onent s, su ch as pro pelle rs an d sha fts m ade f rom m orenob le me tals or al loys.

Anoth er example of galvan ic corrosi onis in aircraft between th e aluminum struc ture and s teel faste ners. Alum inum,highe r on the g alvanic sc ale than s teel, will corro de where t he two met als are in conta ct. To pre vent this, steel fas teners are cadmi um plated to reduce the galvan iceffec t between steel and aluminum. Thus,the m etals in c ontact are aluminum andcadmi um, which are not su bject to s eriousgalva nic attack . Note tha t moderncompo sites, suc h as graph ites, may alsoform galvanic c ouples wit h adjacent dissi milar meta ls and mat erials lea ding tocorro sion deter ioration. The dissim ilarmetal s and comp osite mate rials used inexpos ed equipme nt onboard ships and landvehic les will a lso exhibi t galvanic corrosion .

2.1.2.7 EnvironmentalEmbrittlement and Stress CorrosionCracking

It is well known that metals will corrodeand lose strength faster in the presence oftensile stress and other environmentalconditions. The phenomenon of a

superimposed static tensile stress on acorroding metal is known as stress corrosion.The rapid deterioration of high strengthaircraft alloys by stress corrosion, hydrogenembrittlement, and mercury embrittlementfall into this category of corrosion. Thistype of corrosion occurs by the combinedand simultaneous action of corrosion and astatic tensile stress. Neither stress norcorrosion acting separately would cause suchdamage.

Unf ortun ately , all of t he hi gh st rengt haer ospac e all oys, inclu ding alumi num, steel and tita nium, are susce ptibl e to this typeof attac k in such envir onmen ts as fres hwat er, m oist air, sea w ater and o ther non-spe cific mild envi ronme nts. Certa in al loys, par ticul arly those of t itani um, d o not cor rode or pi t in fresh or s alt w ater atamb ient tempe ratur es, s o tha t smo othspe cimen s of such alloy s do not e xperi encestr ess c orros ion i n the se en viron ments .Env ironm ental embr ittle ment and s tress cor rosio n cra cking are found in a ircra ft,shi ps an d lan d veh icles wher e the expo sedstr uctur e is also under cons tant or cy clicstr ess.

2.1.2.8 Corrosion FatigueWhereas stress corrosion or

environmental embrittlement requires anenduring tensile stress, metallic failure due tocorrosion fatigue is caused by cyclicstressing in mildly corrosive environments.The speed of failure for corrosion fatigue iscyclic dependent and not directly dependentupon the time of exposure. In general, ametal can withstand an infinite number ofstress cycles if the stress does not exceed acertain value, called the fatigue or endurancelimit. If the same metal is subjected toalternating or cyclic stresses in a corrosiveenvironment, fatigue cracking will occur


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much more readily, and a fatigue orendurance limit is no longer accurate.

Cyclic loading that leads to fatigueoccurs in many ways on modern airframes.Some of these are: airborne maneuvers,vibrations (especially in helicopters), gustloadings, and cabin pressurization cycles.

2.1.2.9 Combined MechanismsSom e tim e dep enden t mec hanis ms,

suc h as pitti ng an d exf oliat ion, can s erve toini tiate fail ures by st ress corro sion and/o rcor rosio n fat igue. For examp le, c orros iontha t beg ins a s pit ting on a helic opter blad ecan lead to s tress corr osion at t hat p oint asthe blad e is loade d in fligh t. Cy clic loads ,

inc ludin g vib ratio ns, c an ac celer ate t hefat igue proce ss, w hich can t hen l ead t oult imate fail ure o f the comp onent .

2.1.2.10 SummaryCorrosion of metal in military systems is

a highly complex phenomenon and takesmany different forms. The result of allcorrosion is the loss of strength of thematerial and the structure. Understanding thevarious forms and combinations of corrosionis essential to determining the importance ofeach and to finding the most appropriatetechnologies for detection andcharacterization of corrosion.


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Table 2.1 summarizes the types ofcorrosion that can damage structures, andtheir characteristics.

2.1.3 Factors Affecting CorrosionThe various processes of corrosion are

affected by several factors. Among these arethe type of material selected for theapplication, the heat treatment of thematerial, the environment of the application,and the presence of any contaminants in the

material itself.

2.1.3.1 Effect of Material SelectionA fundamental factor in corrosion is the

susceptibility of the material itself. High-strength, heat-treatable aluminum alloys aresusceptible to intergranular corrosion as wellas to pitting and general attack. Allmagnesium alloys are highly susceptible togeneral and pitting attack when exposed tocorrosive environments. Materials must beselected primarily on the basis of structural

Table 2-1. Corrosion Types and Characteristics.

CorrosionType


UniformAttack

Exposure to corrosiveenvironment

Irregular rougheningof the exposedsurface

Scale, metallic salts

Pitting Impurity or chemicaldiscontinuity in the paint orprotective coating

Localized pits orholes withcylindrical shape andhemisphericalbottom

Rapid dissolution of thebase metal

Inter-granular orExfoliation

Presence of strong potentialdifferences in grain or phaseboundaries

Appears at the grainor phase boundariesas uniform damage

Produces scale typeindications at smallermagnitude than stresscorrosion

Crevice Afflicts mechanical joints,such as coupled pipes orthreaded connections.Triggered by local differencein environment composition(Oxygen concentration)

Localized damage inthe form of scale andpitting

Same as scale and pitting.May induce stress due toexpansion of the corrosionproduct. In lap splices, thisis called “pillowing.”

Filiform High humidity aroundfasteners, skin joints orbreaks in coating cause anelectrolytic process

Fine, meandering,thread-like trenchesthat spread from thesource

Similar to scale. Lifting ofthe coating.

GalvanicCorrosion

Corrosive condition thatresults from contact ofdifferent metals

Uniform damage,scale, surface foggingor tarnishing

Emission of mostlymolecular hydrogen gas in adiffused form

StressCorrosion

Mechanical tensile stressescombined with chemical

Micro-macro-crackslocated at shielded or

Initially produces scale-type indications


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efficiency; therefore, corrosion resistance isat times a secondary consideration at thedesign level. Use of more corrosion resistantmaterials normally involves additionalweight, which is considered to outweigh thecost of preventing corrosion by propermaintenance or by chemical surfacetreatments and finishes.

2.1.3.2 Effect of Heat TreatmentHeat treatment of the alloy is a vital

factor in establishing resistance to corrosionand is a factor over which definite control isexercised. A rigid inspection procedure ismaintained, for both the heat-treatingprocesses and the facilities used, to ensureproper heat treatment. To make certain thatreplacement parts meet the heat-treatingspecifications, it is essential that parts beprocured either directly from themanufacturer or from approved sources, andthat heat-treatment processes be controlledat qualified repair facilities.

2.1.3.3 Effect of EnvironmentExposure to salt water, moisture

condensate, chemicals, and soil and dust inthe atmosphere affect the degree ofcorrosion. The geographical flight routes andbases of operation will expose someairplanes to more corrosive conditions thanothers. The same is true of ships and landvehicle fleets. Ships operated in fresh waterdo not deteriorate as quickly as similarvessels operated in salt water. The truckfleets positioned in Hawaii and the Pacificare significantly more damaged by corrosionthan those in Europe, for instance. Corrosionprevention and control requirements (andtherefore detection equipment) will varyfrom one area to another.

2.1.3.4 Effect of ContaminationA corrosive action can result when a

contaminating material comes into contact

with a metal surface; the degree of corrosiveaction is determined by the composition ofsuch contaminating materials and the length oftime they remain in contact. The extent ofcorrosive attack can be minimized by frequentcleaning to remove contaminating deposits. Inaddition, anodic and chemical treatments aswell as proper paint finishes should bemaintained in clean and intact condition. Theprimary purpose of these coatings is toprovide a barrier and temporarily to preventthe corrosive media from contacting theunderlying metal, thereby allowing time fortheir removal by periodic washing.

2.2Corrosion Detection TechnologyAreas

This study will concentrate on fivecorrosion detection technology areas: 1)visual/optical, 2) electromagnetic eddycurrent, 3) acoustic ultrasonic, 4)radiographic, and 5) thermographic. Theseare the five most mature technology areas.

2.2.1 VisualVisual inspection is the oldest and most

common form of NDI used to inspectaircraft for corrosion. The physical principlebehind visual inspection is that visible lightis reflected from the surface of the part tothe inspector’s eyes. By observing theappearance of the part, the inspector caninfer its condition. Visual inspection is aquick and economical method of detectingvarious types of defects before they causefailure. Its reliability depends upon theability and experience of the inspector. Theinspector must know how to search forcritical flaws and how to recognize areaswhere failure could occur. The human eye isa very discerning instrument and, withtraining, the brain can interpret images muchbetter than any automated device.


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Optical devices are available to aid thenaked eye in visual inspection and flawdetection. This equipment can be used tomagnify defects that could not be seen bythe unaided eye or to permit inspection ofareas otherwise hidden from view.

Visual inspection is often conductedusing a strong flashlight, a mirror mountedon a ball joint, and a magnifying aid.Magnifying aids range in power from 1.5Xto 2,000X. Fields of view typically rangefrom 3.5 to 0.006 inches with resolutionsranging from 0.002 to 0.000008 inches. A10X magnifying glass is recommended forpositive identification of suspected cracks orcorrosion. Other inspection methods, suchas eddy current, ultrasonic and others, can beused to verify questionable indications.

2.2.1.1 Techniques andTechnologiesBorescopes: A borescope is a long, thin,rigid rod-like optical device that allows aninspector to see into inaccessible areas bytransmitting an image from one end of thescope to the other. Certain structures, suchas engines, are designed to accept theinsertion of borescopes for the inspection ofcritical areas. A borescope can be thought ofas a highly specialized periscope that canfocus at extremely close distances.

A borescope works by forming an imageof the viewing area with an objective lens.That image is transferred along the rod by asystem of intermediate lenses. The imagearrives at the ocular lens, which creates aviewable virtual image. The ocular can befocused for comfortable viewing. Borescopestypically range from 0.25 to 0.50 inches indiameter and can be as long as six feet.Borescopes often incorporate a light near theobjective lens to illuminate the viewing area.Different borescopes are designed to provide

direct, forward oblique, right angle andretrospective viewing of the area in question.

Fiberscopes: Fiberscopes are bundles offiber optic cables that transmit light fromend to end. They are similar to borescopeswith the difference that they are flexible.They can be inserted into openings andcurled into otherwise inaccessible areas.They also incorporate light sources forillumination of the subject area and devicesfor bending the tip in the desired direction.Like the borescope, fiberscope images areformed at an ocular or eyepiece.

Video imaging systems: Video imagingsystems (or “videoscopes”) consist of tinycharge coupled device (CCD) cameras at theend of a flexible probe. Borescopes,fiberscopes and even microscopes can beattached to video imaging systems. Thesesystems consist of a camera to receive theimage, processors, and a monitor to view theimage. The image on the monitor can beenlarged or overlaid with measurement scales.Images can also be printed on paper or storeddigitally to obtain a permanent record.

2.2.1.2 Advantages andDisadvantages

Surface corrosion, exfoliation, pitting andintergranular corrosion can be detectedvisually when proper access to the inspectionarea is obtained. Obviously, visual inspectioncan only detect surface anomalies. However,some internal corrosion processes do exhibitsurface indications, such as pillowing orflaking. The primary advantages of visualinspection include its ability to be performedquickly and inexpensively without the needfor complicated equipment. Modest trainingis required, and typically no special safetyprecautions need to be taken. Wherenecessary, permanent records can be obtainedby photography or digital imaging and stored.


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The disadvantage of visual inspection isthat the surface to be inspected must berelatively clean and accessible to either thenaked eye or to an optical aid such as aborescope. Typically, visual inspectionlacks the sensitivity of other surface NDImethods. Further, visual methods arequalitative and do not provide quantitativeassessments of either material loss orresidual strength. Additionally, visualinspection techniques can be man-hourintensive and monotonous, leading to errors.

2.2.1.3 Current ResearchAdvanced visual inspection methods

include moiré and structured-light-basedoptical profilometry, Diffracto Sight (apatented process developed by Diffracto,Ltd. of Canada), “edge of light”, and videoimage enhancement analysis. Moiré andstructured light are methods to visualize andquantify surface height irregularities.Diffracto Sight is a surface slopevisualization technique. Video imageprocessing is a computer-based methodologyfor enhancing and analyzing video images forflaw detection. The most promisingapplications for these advanced visualtechniques are detection and classification ofcorrosion-induced paint liftoff and pillowinginduced by corrosion between frayingsurfaces and in areas that would normallyrequire disassembly. Diffracto Sight, or D-Sight as it is known, is in the process ofcommercialization.

Moiré interferometry is a family oftechniques that visualize surface irregularities.Many variations are possible, but thetechnique most applicable to corrosiondetection is shadow moiré (sometimes calledprojection moiré) for surface heightdetermination. The Naval Air DevelopmentCenter has developed a hand-held test system

that employs shadow moiré for fieldinspection of possible damage sites incomposite structures on aircraft. A projectionmoiré system built and marketed by WYKOCorp. of Tucson, Arizona, generates fringesinterferometrically and uses a fringe shiftalgorithm to compute the surface contour.Improvements in CCD camera resolutionshould improve height resolution beyond thecurrent 0.01 inches.

The structured light technique isgeometrically similar to projected or shadowmoiré methods, and can be thought of as anoptical straight edge. Instead of fringecontours being the resultant observation, thedeparture from straightness of a projectedline is the observable. Using imageprocessing techniques, the surface profilecan be calculated.

D-Sight has the potential to map areas ofsurface waviness as well as identify cracks,depressions, evidence of corrosion and othersurface anomalies. D-Sight is a method bywhich slope departures from an otherwisesmooth surface are visualized as shadows. Itcan be used in direct visual inspection orcombined with photographic or videocameras and computer-aided imageprocessing. The concept of D-Sight is relatedto the schlieren method for visualizing indexof refraction gradients or slopes in an opticalsystem.

One possible problem with D-Sight isthat the technique shows virtually everydeviation on the surface, regardless ofwhether it is a defect or a normal result ofmanufacture. This statement is true of alloptical/visual techniques. The more sensitivethe technique, the more it will show. Thekey then is the ability to distinguish betweenthese surface deviations. In this respect,enhanced visual techniques are similar to


14

Optical devices are available to aid thenaked eye in visual inspection and flawdetection. This equipment can be used tomagnify defects that could not be seen bythe unaided eye or to permit inspection ofareas otherwise hidden from view.

Visual inspection is often conductedusing a strong flashlight, a mirror mountedon a ball joint, and a magnifying aid.Magnifying aids range in power from 1.5Xto 2,000X. Fields of view typically rangefrom 3.5 to 0.006 inches with resolutionsranging from 0.002 to 0.000008 inches. A10X magnifying glass is recommended forpositive identification of suspected cracks orcorrosion. Other inspection methods, suchas eddy current, ultrasonic and others, can beused to verify questionable indications.

2.2.1.1 Techniques andTechnologiesBorescopes: A borescope is a long, thin,rigid rod-like optical device that allows aninspector to see into inaccessible areas bytransmitting an image from one end of thescope to the other. Certain structures, suchas engines, are designed to accept theinsertion of borescopes for the inspection ofcritical areas. A borescope can be thought ofas a highly specialized periscope that canfocus at extremely close distances.

A borescope works by forming an imageof the viewing area with an objective lens.That image is transferred along the rod by asystem of intermediate lenses. The imagearrives at the ocular lens, which creates aviewable virtual image. The ocular can befocused for comfortable viewing. Borescopestypically range from 0.25 to 0.50 inches indiameter and can be as long as six feet.Borescopes often incorporate a light near theobjective lens to illuminate the viewing area.Different borescopes are designed to provide

direct, forward oblique, right angle andretrospective viewing of the area in question.

Fiberscopes: Fiberscopes are bundles offiber optic cables that transmit light fromend to end. They are similar to borescopeswith the difference that they are flexible.They can be inserted into openings andcurled into otherwise inaccessible areas.They also incorporate light sources forillumination of the subject area and devicesfor bending the tip in the desired direction.Like the borescope, fiberscope images areformed at an ocular or eyepiece.

Video imaging systems: Video imagingsystems (or “videoscopes”) consist of tinycharge coupled device (CCD) cameras at theend of a flexible probe. Borescopes,fiberscopes and even microscopes can beattached to video imaging systems. Thesesystems consist of a camera to receive theimage, processors, and a monitor to view theimage. The image on the monitor can beenlarged or overlaid with measurement scales.Images can also be printed on paper or storeddigitally to obtain a permanent record.


Surface corrosion, exfoliation, pitting andintergranular corrosion can be detectedvisually when proper access to the inspectionarea is obtained. Obviously, visual inspectioncan only detect surface anomalies. However,some internal corrosion processes do exhibitsurface indications, such as pillowing orflaking. The primary advantages of visualinspection include its ability to be performedquickly and inexpensively without the needfor complicated equipment. Modest trainingis required, and typically no special safetyprecautions need to be taken. Wherenecessary, permanent records can be obtainedby photography or digital imaging and stored.


15

The disadvantage of visual inspection isthat the surface to be inspected must berelatively clean and accessible to either thenaked eye or to an optical aid such as aborescope. Typically, visual inspectionlacks the sensitivity of other surface NDImethods. Further, visual methods arequalitative and do not provide quantitativeassessments of either material loss orresidual strength. Additionally, visualinspection techniques can be man-hourintensive and monotonous, leading to errors.

2.2.1.3 Current ResearchAdvanced visual inspection methods

include moiré and structured-light-basedoptical profilometry, Diffracto Sight (apatented process developed by Diffracto,Ltd. of Canada), “edge of light”, and videoimage enhancement analysis. Moiré andstructured light are methods to visualize andquantify surface height irregularities.Diffracto Sight is a surface slopevisualization technique. Video imageprocessing is a computer-based methodologyfor enhancing and analyzing video images forflaw detection. The most promisingapplications for these advanced visualtechniques are detection and classification ofcorrosion-induced paint liftoff and pillowinginduced by corrosion between frayingsurfaces and in areas that would normallyrequire disassembly. Diffracto Sight, or D-Sight as it is known, is in the process ofcommercialization.

Moiré interferometry is a family oftechniques that visualize surface irregularities.Many variations are possible, but thetechnique most applicable to corrosiondetection is shadow moiré (sometimes calledprojection moiré) for surface heightdetermination. The Naval Air DevelopmentCenter has developed a hand-held test system

that employs shadow moiré for fieldinspection of possible damage sites incomposite structures on aircraft. A projectionmoiré system built and marketed by WYKOCorp. of Tucson, Arizona, generates fringesinterferometrically and uses a fringe shiftalgorithm to compute the surface contour.Improvements in CCD camera resolutionshould improve height resolution beyond thecurrent 0.01 inches.

The structured light technique isgeometrically similar to projected or shadowmoiré methods, and can be thought of as anoptical straight edge. Instead of fringecontours being the resultant observation, thedeparture from straightness of a projectedline is the observable. Using imageprocessing techniques, the surface profilecan be calculated.

D-Sight has the potential to map areas ofsurface waviness as well as identify cracks,depressions, evidence of corrosion and othersurface anomalies. D-Sight is a method bywhich slope departures from an otherwisesmooth surface are visualized as shadows. Itcan be used in direct visual inspection orcombined with photographic or videocameras and computer-aided imageprocessing. The concept of D-Sight is relatedto the schlieren method for visualizing indexof refraction gradients or slopes in an opticalsystem.

One possible problem with D-Sight isthat the technique shows virtually everydeviation on the surface, regardless ofwhether it is a defect or a normal result ofmanufacture. This statement is true of alloptical/visual techniques. The more sensitivethe technique, the more it will show. Thekey then is the ability to distinguish betweenthese surface deviations. In this respect,enhanced visual techniques are similar to


16

radiographs, which display many featuresand it is up to trained inspectors todistinguish between normal and defectsignatures. In fact, because D Sight showsuch detail, it is possible to characterizedifferent surface anomolies to reduce thenumber of false calls. D-Sight may be mostuseful to survey large areas relatively quicklyto identify specific areas for inspection bymore detailed methods.

The Institute for Aerospace Research(IAR), National Research Council Canada(NRCC), has developed a new enhancedoptical technique. this technique is based onoptical scanning of the surface using a lightsource passing through a slit and reflectedfrom the inspected surface at a grazing angleto a CCD matrix. This technique needs acomputer for image reconstruction. EOLresolution for lap joint corrosion is similar tothat of D Sight. The technique is slower thanarea D Sight; however, it is better suited forautomated interpretation and quantificationof corrosion in areas identified by othermethods.

EOL has been shown to be very effectivein detecting small surface cracks. In a studycomparing various NDI methods ofinspection of turbine disk for bolt cracking,EOL has demonstrated higher POD than UTand penetrant methods while it was onlyslightly inferior to manual Eddy Current(90/95 length of 1.36 mm for EOL vs. 0.84mm for EC).

Video image enhancement relies on digitalimage processing to capture and enhanceimages so that a human inspector might havebetter imagery to deal with and makejudgments upon. Image processing permitsthe freeze-frame capture, enhancement, anddisplay of an image. Additionally,processing algorithms may be applied which

could identify, measure, and classify defectsor objects of interest.

2.2.2 Eddy CurrentWhen an electrically conductive material

is exposed to an alternating magnetic fieldthat is generated by a coil of wire carrying analternating current, eddy currents are inducedon and below the surface of the material.These eddy currents, in turn, generate theirown magnetic field which opposes themagnetic field of the test coil. This magneticfield interaction causes a resistance ofcurrent flow, or impedance, in the test coil.By measuring this change in impedance, thetest coil or a separate sensing coil can beused to detect any condition that wouldaffect the current carrying properties of thetest material.

Eddy currents are sensitive to changes inelectrical conductivity, changes in magneticpermeability (the ability of a material to bemagnetized), geometry or shape of the partbeing analyzed, and defects. Among thelatter defects are cracks, inclusions, porosityand corrosion.

2.2.2.1 Techniques andTechnologies

Most modern eddy current instrumentsin use today are relatively small and batterypowered. In general, surface detection isaccomplished with probes containing smallcoils (0.10 inch diameter) operating at a highfrequency, generally 100 kHz and above.Low frequency eddy current (LFEC) is usedto penetrate deeper into a part to detectsubsurface defects or cracks in underlyingstructure. The lower the frequency, thedeeper the penetration. LFEC is generallyconsidered to be between 100 Hz and 50kHz.


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Initially, eddy current devices utilized ameter to display changes of voltage in thetest coil. Currently, phase analysisinstruments provide both impedance andphase information. This information isdisplayed on an oscilloscope or an integratedLCD display on the instrument. Resultsfrom eddy current inspections are obtainedimmediately.

A meter type of eddy current devicemust be calibrated against a knowncalibration block. The instrument is zeroedagainst a good portion of the block. Theprobe is then positioned over a crack ofknown size, and the meter deflection isadjusted accordingly.

The other type of eddy currentinstrument displays its results on planarform on a screen. This format allows bothcomponents of the coil’s impedance to beviewed. One component consists of theelectrical resistance due to the metal path ofthe coil wire and the conductive test part.The other component consists of theresistance developed by the inductedmagnetic field on the coil’s magnetic field.The combination of these two componentson a single display is known as animpedance plane. It should be noted thatproper interpretation of an impedance planedisplay requires extensive knowledge of alleddy current principles and therefore propertraining.

Eddy current testing is used extensivelyto detect cracks, heat damage and corrosionthinning. HFEC is used to detect exfoliationcorrosion around installed fasteners.Inspection is usually directed at specificsmall areas rather than large areas.


A major advantage of the eddy currentmethod is that it requires only minimum partpreparation. Reliable inspections can beperformed through normal paint ornonconductive materials up to thicknesses ofapproximately 0.015 inch. Eddy currenttechnology can be used to detect surface andsubsurface flaws on single and multiplelayered materials. It is sensitive to smalldefects and thickness changes. It is low costcompared to other NDI techniques, canproduce a permanent record and ismoderately fast. Eddy current testers areportable.

On the other hand, there are a number offactors which should be taken into account,including:

• The surface to be inspected must beaccessible to the eddy current probe

• Rough surfaces may interfere with thetest

• Tests can only be performed onconductive materials

• Much skill and training are required

• Reference standards are needed forcomparison

• The depth of penetration is limited bythe frequency of the probe

• It is a time consuming method for largeareas.

Eddy current is one of the most sensitiveand reliable methods for detecting surfaceand subsurface flaws. Its applicationrequires considerable skill, demanding trainedand qualified personnel to achieve a highdegree of reliability.


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2.2.2.3 Current ResearchScanned Pulsed Eddy Current. Thistechnique for application of eddy currenttechnology employs analysis of the peakamplitude and zero crossover of theresponse to an input pulse to characterizethe loss of material. This technology hasbeen shown to reliably detect and measurematerial loss on the bottom of a top layer,the top of a bottom layer, and the bottom ofa bottom layer in two-layer samples.Material loss is displayed according to acolor scheme to an accuracy of about fivepercent. A mechanical bond is not necessaryas it is with ultrasonic testing. Theinstrument and scanner are rugged andportable, using conventional coils andcommercial probes. The technique issensitive to hidden corrosion and cracks andprovides a quantitative determination ofmetal loss. The time gating featurediscriminates against fasteners and liftoff,and provides an indication of which surfacein a multi-layer structure is suspect. Theprogress here is in the control of the eddycurrent probe through a computer-controlledscanning mechanism and the processing ofthe sensed data into C-scan, or two-dimensional, images of the inspected surface.

Mobile Automated Scanner (MAUS). TheMobile Automated Scanner, currently in itsthird generation, was developed byMcDonnell Douglas (now Boeing) undercontract to the U.S. Air Force. MAUS III is aportable C-scan inspection system thatintegrates several traditional inspectiontechniques into a single package. Detectioncapabilities include pulse echo ultrasonics,ultrasonic resonance, eddy current, andexternal DC voltages. Inspection applicationsinclude metallics, monolithic composites,hybrid composite/metallic, and bonded

structures. The improvement represented inthis piece of equipment is the integration ofseveral separate techniques into a singlepackage and the ability to scan larger areasquickly and efficiently. Boeing is coming outwith a MAUS IV line.

Magneto-Optic Eddy CurrentImaging (MOI). MOI images result fromthe response of the Faraday magneto-opticsensor to weak magnetic fields that aregenerated when eddy currents induced bythe MOI interact with defects in theinspected material. Images appear directly atthe sensor and can be viewed directly orimaged by a small CCD camera locatedinside the imaging unit. The operator viewsthe image on the video monitor while movingthe imaging head continuously along the areato be inspected. In contrast to conventionaleddy current methods, the MOI imagesresemble the defects that produce them,making the interpretation of the results moreintuitive than the interpretation of traces ona CRT screen. Rivet holes, cracks andsubsurface corrosion are readily visible. Theimage is in video format and therefore easilyrecorded for documentation.

2.2.3 UltrasonicUltrasonic inspection utilizes high-

frequency sound waves as a means ofdetecting discontinuities in parts. Ultrasonic(above human hearing range) sound wavesare sent into the material to be examined.The waves travel through the materials andare reflected from the interfaces, such asinternal defects and the back surface of thematerial. The reflected beam is displayed andanalyzed to determine the condition of thepart.

Ultrasonic testing is accomplished bysending an electrical pulse to a transducer.


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This pulse causes the transducer to send apulse of high frequency sound into the part.A coupling medium, such as water, betweenthe transducer and the material is required.This pulse travels through the material untilit reflects from a discontinuity or from aback surface. The reflected pulse is receivedby the transducer and converted back into anelectrical signal. This signal is displayed onan oscilloscope for analysis. By examiningthe variations of a given response pattern,discontinuities are identified.


Techniques have been developed toemploy different kinds of waves, dependingon the type of inspection desired.Longitudinal waves, also called compressionwaves, are the type most widely used. Theyoccur when the beam enters the surface at anangle near 90 degrees. These waves travelthrough materials as a series of alternatecompressions and dilations in which thevibrations of the particles are parallel to thedirection of the wave travel. This wave iseasily generated, easily detected, and has ahigh velocity of travel in most materials.Longitudinal waves are used for thedetection and location of defects that presenta reasonably large frontal area parallel to thesurface from which the test is being made,such as for corrosion loss and delaminations.They are not very effective, however, for thedetection of cracks which are perpendicularto the surface.

Shear waves (transverse waves) are alsoused extensively in ultrasonic inspection andare generated when the beam enters thesurface at moderate angles. Shear wavemotion is similar to the vibrations of a ropethat is being shaken rhythmically; particlevibration is perpendicular to the direction of

propagation. Unlike longitudinal waves,shear waves do not travel far in liquids.Shear waves have a velocity that is about 50percent of longitudinal waves in the samematerial. They also have a shorterwavelength than longitudinal waves, whichmakes them more sensitive to smallinclusions. This also makes them more easilyscattered and reduces penetration.

Surface waves (Rayleigh waves) occurwhen the beam enters the material at ashallow angle. They travel with littleattenuation in the direction of thepropagation, but their energy decreasesrapidly as the wave penetrates below thesurface. They are affected by variations inhardness, plated coatings, shot peening, andsurface cracks, and are easily dampened bydirt or grease on the specimen.

Lamb waves, also known as plate wavesand guided waves, occur when ultrasonicvibrations are introduced at an angle into arelatively thin sheet. A Lamb wave consistsof a complex vibration that occursthroughout the thickness of the material,somewhat like the motion of surface waves.The propagation characteristics of Lambwaves depend on the density, elasticproperties, and structure of the material aswell as the thickness of the test piece andthe frequency of vibrations. There are twobasic forms of Lamb waves: symmetrical(dilational) and asymmetrical (bending). Eachform is further subdivided into severalmodes having different velocities that can becontrolled by the angle at which the wavesenter the test piece. Lamb waves can be usedfor detecting voids in laminated structures,such as sandwich panels and other thin,bonded, laminated structures.


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The advantages of using ultrasonicinspection techniques include:

• Its versatility in requiring access to onlyone surface of the specimen and the widerange of materials and thicknesses thatcan be inspected

• Rapid response of the system,

• The capability of automating theinspection application

• Accuracy in determining flaw positionand size

• High sensitivity permitting detection ofminute defects

• Detection of both surface and subsurfaceflaws

• Permanent data storage

• Minimal part preparation and specialsafety precautions.

Ultrasonic inspection yields immediateresults which can be viewed on anoscilloscope or detected audibly, enabling arelatively rapid rate of inspection. Contacttype ultrasonic equipment is highlyportable, hand held, and lightweight.

The disadvantages of the ultrasonic testmethod are that, except for simple thicknessmeasurements, it requires a high degree ofexperience and skill to set up the inspectionand interpret the results, and both couplantand reference standards are required.

2.2.3.3 Current ResearchDripless Bubbler. One of the mostpromising improvements to ultrasonictesting technology is the dripless bubbler.This is a development not in the ultrasonicprobe itself but in the mechanism for

employing it consistently on curved,irregular, vertical, and inverted surfaces. Thedripless bubbler itself is a pneumaticallypowered device to hold a water columnbetween the ultrasonic probe and inspectedsurface. With software control of themovement of the probe, a fast and accuratemap of the inspected surface can beobtained. Thus the progress is in theefficient manipulation of the sensor and therapid processing of the data for furtherhuman analysis. The dripless bubbler is adevelopment of the Iowa State UniversityCenter for Nondestructive Evaluation(CNDE).

Laser Ultrasound. There is also emerginginterest in the area of laser ultrasonics, orlaser-based ultrasound (LUS). Theinnovation is in the use of laser energy togenerate sound waves in a solid. Thisobviates the need for a couplant between thetransducer and the surface of the inspectedmaterial. The initial application of this newtechnology seems to be directed towardprocess control. Regardless, the technologydoes have application for thicknessmeasurement, inspection of welds and joints,surface and bulk flaw detection on a varietyof materials, and characterization ofcorrosion and porosity on metals. TheDepartment of Energy is in the formativestages of developing and sponsoring a LUSresearch program. This technology is in thelaboratory stage. In Canada, the IndustrialMaterials Institute of NRCC, in partnershipwith NRCC/IAR, has been developing laserUT for corrosion detection since 1996. Lapjoint corrosion and exfoliation in thicksection aluminum alloys are being addressedin a program sponsored by the CanadianDND.


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2.2.4 RadiographyRadiographic inspection is a

nondestructive method of inspectingmaterials for surface and subsurfacediscontinuities. This method utilizes radiationin the form of either x-rays or gamma rays,both of which are electromagnetic waves ofvery short wavelength. The waves penetratethe material and are absorbed, depending onthe thickness or the density of the materialbeing examined. By recording the differencesin absorption of the transmitted waves,variations on the material can be detected.The variations in transmitted waves may berecorded by either film or electronic devices,providing a two-dimensional image thatrequires interpretation. The method issensitive to any discontinuities that affect theabsorption characteristics of the material.

Neutron radiography is a special purposeform of radiography that employs highenergy neutrons to penetrate structures andmaterials to form similar images, either onfilm or displays, of the internal structures andpossible defects due to cracks and corrosion.


The techniques and technologies ofradiography have most to do with the designof the x-ray tube itself. There are manydifferent types of tubes used for specialapplications. The most common is thedirectional tube, which emits radiationperpendicular to the long axis of the tube in acone of approximately 40 degrees. Anothertype is the panoramic tube, which emits x-rays in a complete 360 degree circle. Thistype of tube would be used, for example, toexamine the girth welds in a jet engine with asingle exposure.

Advanced uses of radiography are beingmade with the aid of computers and high

powered algorithms to manipulate the data.This is termed Computed Tomography, orCT Scanning. By scanning a part from manydirections in the same plane, a cross-sectional view of the part can be generated,and the internal structure may be displayedin a two dimensional view. The tremendousadvantage of this method is that internaldimensions can be measured very accuratelyto determine such conditions as wall thinningin tubes, size of internal discontinuities,relative shapes and contours. More advancedsystems can generate three dimensionalscans when more than one plane is scanned.CT scanning is costly and time consuming.Radiography in general and CT scanning inparticular are extremely useful in validatingand calibrating other, less complex and lesscostly methods.

Radioisotope sources can be used inplace of x-ray tubes. Radioisotopeequipment has inherent hazards, and greatcare must be taken with its use. Only fullytrained and licensed personnel should workwith this equipment. As with x-rays, themost common method of measuring gammaray transmission is with film.

Neutron radiography has foundapplication in Canada and the United States.Neutron radiography requires a high-energyneutron source, such as a nuclear reactor.The high neutron flux makes possible highresolution imaging of relatively largestructures not practical with generator orisotope sources. Neutron radiographyequipment is expensive and entails radiationhazards.


The advantages of radiography includethe detection of both surface and subsurfaceflaws and the ability to use it on all


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materials. It is also a very useful method fordetecting different types of flaws, such ascorrosion, voids, and variations in densityand thickness. All of the test results can berecorded permanently on film.

The disadvantages of radiography are thatoperators require training as interpretation issometimes difficult, orientation of theequipment and the flaw is critical, and theequipment is relatively high in cost. Also,there is no indication of flaw depth unlessmultiple exposures are made. Other factorsinclude that a radiation hazard exists and filmdevelopment time is required.

Since x-rays and gamma rays areexcessively harmful to living tissue, extensivecare must be used during application toprotect nearby personnel and equipment. X-rays and gamma rays cannot be seen, felt, ordetected without special equipment. Tissuedamage can occur without any physicalawareness of the radiation. Protection fromradiation can be obtained with barriers of highdensity materials such as lead or concrete.Protection may also be provided by providinga buffer zone around the radiation source. Theemployment of radiation producing equipmentis sometimes controlled by state or otheragencies.

2.2.4.3 Current ResearchCT scanners are useful for small

component inspections or failure analysis ofassemblies that can fit within the objecthandling capabilities of the scanners. Manyaerospace companies use CT to supporttheir development testing and inspectionefforts. Because of the high cost ofequipment and facilities, CT has not yetbeen employed to a large degree for routineaircraft inspections, including corrosioninspections.

Compton backscatter imaging (CBI) isemerging as a near surface NDI measurementand imaging technique. CBI can detect criticalembedded flaws such as cracks, corrosion anddelaminations in metal and composite aircraftstructures. In CBI, a tomographic image of theinspection layer is obtained by raster scanningthe collimated source-detector assembly overthe object and storing the measured signal as afunction of position. Rather than measuringthe x-rays that pass through the object, CBImeasures the backscattered beam to generatethe image. This enables single-sidedmeasurement.

2.2.5 ThermographyThermography is based on the principle

that a good mechanical bond between twomaterials is also a good thermal bond. Thetemperature distribution on an aircraft skinor component can be measured optically bythe radiation that it produces at infraredwavelengths. Several techniques have beendeveloped that use this temperatureinformation to characterize the thermal - andtherefore the structural - properties of thesample being tested.

Many defects affect the thermalproperties of those materials. Examples arecorrosion, debonds, cracks, impact damage,panel thinning, and water ingress intocomposite or honeycomb materials. Byjudicious application of external heat sources,these common aircraft defects can be detectedby an appropriate infrared survey. Severalorganizations have demonstrated techniquesfor infrared structural inspection of aircraft infield tests at maintenance facilities. However,none of these techniques is at present inwidespread use in the aviation field. Use ofthermography techniques currently rangefrom laboratory investigations to fieldedequipment. The more advanced systems are


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in the prototype stage, and their design andoperational feasibility for use on transportaircraft are being evaluated.

Thermography in its basic form does notseem to be widely employed. An advancedthermographic NDI system can bepurchased directly or assembled fromcomponents purchased from a variety ofsources. Due to the cost of infrareddetectors, the cost of a system will be in the$100K to $300K range. Because of the highprice and the lack of original equipmentmanufacturer (OEM) and regulatoryapproval for use of these methods, sales foraircraft maintenance inspections have beenlimited.

2.2.5.1 Current ResearchWayne State University and Thermal

Wave Imaging, Inc. perform research in thearea of thermal wave imaging. This technologyuses heat pulses to inspect subsurface featuresof solid objects. The thermal pulses areproduced by flash lamps. Pulse reflections arerecorded and viewed in the time domain muchlike ultrasonics. This technology can be usedto assess impact damage, disbonds anddelaminations in composites, and corrosiondamage. It provides quantitative thicknessmeasurement of the inspected material.

The raw image displayed by an IR cameraonly conveys information about thetemperature and emissivity of the surface ofthe target it views. To gain information aboutthe internal structure of the target, it isnecessary to observe the target as it is eitherbeing heated or as it cools. Since it takes heatfrom the surface longer to reach a deeperobstruction than a shallow one, the effect ofthe shallow obstruction appears at thesurface earlier than that of a deep one. Youcan think of this as a thermal pulse generatedat the front surface, which is then “reflected”

off the back surface or a subsurface defect.The thermal response to a pulse over time,color coded by time of arrival, is displayed asa two dimensional, C-scan image forinterpretation by the operator.

This technology is being marketed underthe name EchoTherm by Thermal WaveImaging, Inc., which was originally created asa small spin-off from Wayne StateUniversity. It shows promise as a non-intrusive means of inspecting fairly largeareas efficiently.

Lawrence Livermore NationalLaboratory is working in the area of dual-band infrared computed tomography (DBIR-CT). This technique uses flash lamps toexcite the material with thermal pulses anddetectors in both the 3-5 and 8-12 micronrange to obtain the results. The DBIR-CTtechnique gives three-dimensional, pulsed-IRthermal images in which the thermalexcitation provides depth information, whilethe use of tomographic mapping techniqueseliminates deep clutter. This technique iscomputer-intensive and should be consideredan extension of the thermal wave imagingtechnique described above.


Thermography, in its basic form, has thelimitation of measuring only the surfacetemperature of the inspected structure orassembly. As such, it does not providedetailed insight into defects or material losslocated more deeply in the structure. Becauseit is an area-type technique, it is most usefulfor identifying areas that should be inspectedmore carefully using more precise techniques,such as eddy current and ultrasonic methods.

Therm al wave im aging over comes some of th ese limita tions by m easuring t he time


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respo nse of a t hermal pul se rather than thetempe rature res ponse. The thermal p ulsepenet rates mult iple layer s where th ere is agood mechanical bond betw een the la yers.The b enefits of thermal w ave imagin gtechn ology incl ude the ab ility to s can awide area quick ly and pro vide fast, quant itatively defined fe edback wit hminim al operato r interpre tation req uired.Propo nents stat e that the rmal wave imagesare e asier to i nterpret t han images based onoptic al interfe rence meth ods. Therm al waveimagi ng does no t require an electri callycondu ctive stru cture and can be emp loyedon al uminum, pl astics, st eel, andcompo sites such as graphi te epoxy. It isless effective when deali ng with hi ghlyinsul ating mate rials like rubber or glass.

As would be expected, defects moredeeply contained within the structureproduce blurred images compared to thoseclose to the surface. Additionally, highlyreflective surfaces must be coated with aspecial solution that will absorb the IR lightof the flash lamps and will also providebetter emissivity of the response pulse forthe IR cameras.

The disadvantages of thermal waveimaging relate to its precision and cost.Complexity is also a factor in that thesystem is not a single, self-contained unit.Thermal wave imaging is currently an areatechnique that must be followed up withpoint techniques, such as eddy current andultrasonic methods. With greater fieldexperience, this limitation may diminish. Thecost of a thermal wave imaging system isapproximately $110K per system - $60Kfor the camera and $50K for the othercomponents. In comparison, a single pointultrasound system costs approximately$2.5K and a single point eddy current

system costs about $6K. More advancedtechniques, such as dual band infraredcomputed tomography, are more complex,more expensive and less mature. Judgmentsregarding advantages and disadvantages ofDBIR-CT would be premature.

2.2.6 Other TechnologiesThere are several other NDI/NDE

technologies that are useful for discoveringand characterizing defects such as cracks orinclusions. However, these technologies donot lend themselves to application to theproblem of corrosion detection. Thesetechnologies include dye penetrant testing,magnetic particle testing, and acousticemission testing.

One technology that encompasses manyof the individual technologies describedabove is that of data fusion. While notunique to the field of NDE/NDI, data fusionis mentioned by many researchers as havingvery interesting potential. Already, theMAUS is a means for employing twodifferent sensors to the same problem,although not simultaneously. The DBIR-CTcombines two different IR spectra withcomputed tomography to generate threedimensional information. Even so, there isonly isolated instances of data fusionresearch applied to the NDE/NDI and thatonly in certain combinations. Mostresearchers in the field agree that this is anunder-explored area. It does haveimplications of complexity and cost, whichmay have limited its development thus far.

Several researchers are working onembedded sensors that will indicate thepresence of corrosion. One such sensor is athin film device that is used to measure thesmall currents between two metals subject togalvanic corrosion. This device is quite good


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at indicating the presence of a corrosiveenvironment and, by implication, corrosionactivity. To be useful for determination ofmaterial loss, this device would require anextensive data acquisition system todetermine the life history of corrosionexposure. As such, it may be more useful forcorrelating environmental exposure to rate ofcorrosion in a prospective rather thanretrospective sense. Also, evaluation ofadhesives, coatings and sealants may bepossible without long exposure tests.

In addition to sensors themselves, thereis some work being done relative toautomation that has the potential to improvethe productivity of the inspection process.The mobile automated scanning (MAUS)concept was described earlier. In addition,McDonnell Douglas (now Boeing)Aerospace of St. Louis has developed agantry-based automated scanning system.The Automated Ultrasonic Scanning System- Generation Five (AUSS-V) was designedfor inspection of solid laminates andadhesively bonded composite assemblieswhich have complex contoured shapes.AUSS-V provides simultaneous coordinatedcontrol of nine axes of motion to maintainsquirter alignment relative to the inspectionsurface. A three dimensional map of thesurface is generated and used to calculatetrajectories to track the surface duringinspection. The system is able to maintaintransducer alignment within 0.030 inch andis especially useful for complex aerospacecomposite structure inspection.

Current inspection techniques aremanpower intensive. Research into auto-crawlers has demonstrated the potential toimprove this situation. Robotic or remotecontrolled platforms that adhere to theinspection surface using suction cups and

that use various articulation mechanisms formovement have been researched by the JetPropulsion Laboratory of NASA.

If successful, these devices would reduceor obviate the need for complex workplatforms, cherry picker trucks, scaffolding,gantries and other support equipment nowused to gain access to remote areas, such as thetail assemblies of large aircraft. Such crawlerscould carry eddy current, ultrasonic, visual orother sensor devices to perform the actualinspection. These devices could also overcomesome of the human limitations associated withthe repetitive and sometimes boring tasksassociated with inspection. Miniaturization ofboth the sensors and the carrying platformsmay allow access to and inspection of areasthat are now normally inaccessible toconventional forms of inspection. The fueltanks in the outer wing sections of aircraftcome to mind as areas that are difficult orimpossible to inspect otherwise.

2.3Summary

Corrosion detection is a subset of thelarger fields of NonDestructive Evaluationand NonDestructive Inspection. There is anentire professional field associated withNDE/NDI and a related field on corrosionengineering. Corrosion itself is an extremelycomplex subject, and corrosion engineeringcombines several disciplines, includingmechanics, structures, materials science,chemistry, physics, and numerous sensortechnologies. The many forms of corrosionand the attendant damage that results furthercomplicates the subject. Furthermore,corrosion detection is frequently combinedwith other inspection requirements, such ascrack, fatigue and hardness testing.

As more technologies are being exploredfor application to the corrosion detection


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problem, different sensingand measurementmechanisms come into play. Eddy current,ultrasonic, and thermal wave imaging (singlyor in combination) measure electricalimpedance, ultrasonic attenuation, time oftravel, and thermal diffusion that aredependent on the material thickness and anyflaws. Comparative measurements orcalibration of the parameters on knownspecimens enable detection of flaws orestimation of material thickness.Comparison with reference documentationallows the calculation of material lost due tocorrosion. Enhanced visual techniques detectsurface deformations caused by internalformation of corrosion products. Correlationwith known specimens allows the estimationof material volume, and therefore materialthickness, lost due to corrosion.Radiography techniques can provide ameasurable image of the part in question andcan highlight the presence of the products ofcorrosion.

Many of the technologies of NDE/NDIlend themselves to the detection,characterization and quantification ofcorrosion damage. As new materials find usein military systems, the strict definition ofcorrosion being a metallic process may serveto obscure the problem of deterioration incomposite and non-metallic structures.

The larger problem is the aging of militarysystems to the point that they becomeunreliable or even unsafe. We commonly think

of aircraft when considering corrosion becausethey are designed with smaller margins ofsafety and failures tend to be more dramatic.We also tend to think of primary andsecondary structure as the areas most subjectto corrosion. However, engines and even wirebundles experience corrosion and relateddamage. It is safe to say that all militarysystems experience corrosion to some degree.Because military systems are typicallyemployed in hostile and severe environments,corrosion is an ever-present problem.

The users of corrosion detection(NDI/NDE) equipment generally accept agoal of being able to determine 10 percentmaterial loss. This number is somewhatarbitrary and stems from airline experienceas much as anything. The scientificcommunity would like to be able to reliablydetermine material loss in the range of 1percent. As much as anything, this willenable much greater precision in theunderstanding of the RATE of corrosion(and the underlying processes of corrosion,especially in newer materials for which thereis not extensive field experience) andtherefore more accurate predictions of usefulservice life and better recommendations forinspection and maintenance intervals.Therefore, much of the research anddevelopment activities are aimed at thisorder-of-magnitude improvement in theaccuracy of NDE/NDI.

Table 2-2. Summary of Corrosion Detection NDE/NDITechnologies.


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Table 2-2, located to theright, summarizes the majoradvantages anddisadvantages of theprimary corrosion detectionand characterizationtechnologies.

Table 2-3, located on thefollowing page, highlightscorrosion detectiontechnology R&D trends.

The need forquantitative corrosion NDIis clear. The structuralengineering communityrequires corrosion metrics tofeed into analytical modelscapable of assessing theeffect of corrosion damageon residual strength andresidual life of systems.Without quantitativecorrosion NDI techniques,probability of detection datafor NDI techniques cannotbe developed. Quantitativedata are needed forcontinued inspection andmaintenance planning, andfor airworthinessassessments.

3. TECHNOLOGYAPPLICATIONS

Technology Advantages DisadvantagesVisual • Relatively

inexpensive• Large area

coverage• Portability

• Highly subjective• Measurements not precise• Limited to surface inspection• Labor intensive

EnhancedVisual

• Large areacoverage• Very fast• Very sensitive to

lap joint corrosion

• Multi-layer

• Quantification difficult

• Subjective - requires experience

• Requires surface preparation

Eddy Current • Relatively inexpensive

• Good resolution • Multiple layer

capability • Portability

• Low throughput • Interpretation of output • Operator training • Human factors (tedium)

Ultrasonic • Good resolution• Can detect

material loss andthickness

• Single-sided • Requires couplant • Cannot assess multiple layers • Low throughput

Radiography • Best resolution (~1%)

• Image inter-pretation

• Expensive • Radiation safety • Bulky equipment

Thermography

• Large area scan • Relatively high

throughput • “Macro view” of

structures

• Complex equipment • Layered structures are a

problem • Precision of measurements

Robotics andAutomation

• Potential productivity improvements

• Quality assurance • Reliability

Data fusion • Potential accuracy and reliability improvements

• Unproven technology

Sensor fusion • Potential productivity improvements

• Unproven technology

Table 2-3. Corrosion Detection Technology R&D Trends.


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The typical process of finding and

identifying corrosion begins with visualinspection. Clearly, any damage that can beobserved by visual means will require closerinspection. Field inspection by other meansusually entails eddy current and/or ultrasonicinspection. These types of inspections cannormally be accomplished during routinemaintenance without impacting operational

availability. If additional inspection is

determined to be necessary, it is usuallyconducted by specialists under controlledconditions, such as in a protected space or inan NDI laboratory.

Technology Observed Trend Enhanced Visual • Solid film highlighters for consistent and repeatable

reflectivity

• Scanner based systems leading to quanitification ofcorrosion

• Automation of image interpretation to reduce false callrate

Eddy Current • More sophisticated signal and data processing (pulsed eddy current, C-scan imaging)

• More sophisticated sensors (multi-frequency)

Ultrasonic • More efficient scanning methods (dripless bubbler, gantrys, etc.)

• Dry couplants (including laser stimulation)

Radiography • Single-sided methods (backscatter)


Thermography • Time domain analysis (thermal wave imaging)

• Multi-spectral (dual-band infrared)


Robotics and Automation • Attached computer-controlled positioning mechanisms

• Gantrys (multi-axis)

• Crawlers (including vertical and inverted surfaces)

Data fusion • Image processing (color coding, three dimensional, etc.)

• Image correlation (C-scan, etc.)

Sensor fusion • Currently only attempted within a single technology (e.g., eddy current, infrared)

• No observation of research into combining two different sensors into a single probe for simultaneous measurements


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3.1Air Applications

The primary technology application inthe air arena is visual inspection techniques.Maintenance preflight inspections, pilotvisual inspections and maintenance post-flight inspections depend mainly on visualtechniques. Visual techniques are non-quantitative and rely heavily on the expertiseof the individual inspector. Where visualtechniques identify suspicious areas, moreprecise technologies and techniques areemployed. The primary technologies in useare eddy current and ultrasonic. Eddy currentequipment has the advantage of being bothaffordable and portable. Ultrasonicequipment is somewhat encumbered by theparaphernalia associated with the couplantmedium. The following are some of thecommon areas of aircraft that are of specialinterest:

• Control surfaces

• Lap joints

• Surfaces under doubling material

• Fuselage and wing skins and fasteners

• Floorboards, helicopter graphite epoxy

• Bilge, galley, and latrine areas

• Shell and missile casings, and storagecontainers

• Windshield frames

• Access doors.

3.2Sea Applications

Combat ships are very susceptible tocorrosion, as one would expect. There are,however, specific areas on ships that comprisethe top corrosion problems. These include:

• Connectors

• Launchers

• Waveguides

• Cooling Water

• Reflectors

• Radomes

• Grounding Straps

• Vents and Motors

• Pedestals

• Antennas

• Submarine tiles

• Surfaces behind or under insulation

• Composite antenna structures

• High pressure piping

• Gun barrels

• Elevator cable, wire rope

• Boilers

• Condensers

• Propulsion shafting

• Mast fairings

• Bilge, galley, latrine areas

• Shell and missile casings.

3.3Land Applications

Field maintenance of military equipmentsometimes suffers from overemphasis ofcosmetic appearance which may maskserious corrosion problems. The complexityof the structure of many systemscontributes to this problem. For example,cleaning and repainting of trucks and tanksmay hide corrosion problems that existbehind external stowage boxes, ammunitionboxes, and other areas that are not easilyaccessed.

Areas of special interest include:

• Welds and rivets


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• Sheet metal and joints, vehicle cabs

• Shell and missile casings

• Storage container brass plugs

• Artillery fuzes

• Exposed gears and mechanisms

• Armor, depleted uranium.

3.4Summary

The areas where corrosion occurs, thematerials in which it occurs, and theconditions under which it occurs all combineto make the inspection for and detection ofcorrosion a very difficult matter.

4. CORROSION COSTS

As long as corrosion exists, there willalways be some costs attributable to itsprevention and correction. For the purposesof this study, we are primarily interested inthe avoidable costs. Avoidable costs arethose that could be influenced by deliberateinvestment in prevention, detection andcorrection. Decisions regarding avoidablecosts are usually treated as “return oninvestment” economic decisions. Somecommands look for a five-year or betterpayback on corrosion investments.Similarly, any investment that can reducemanpower requirements are especiallyappealing, particularly in manpower limitedsituations, such as onboard ships.

The point at which any system shouldbe retired, whether it is a transport aircraftor a personal automobile, is a complexdetermination. In general, replacement willoccur when the system or item of equipmentreaches the point of economical repair, i.e.,when the cost to repair exceeds somefraction of the cost of replacement. This

fraction will be influenced by military need,and military need has kept many systems inthe active inventory much longer thanplanned for initially.

Furthermore, the decision to retire anitem of equipment may be driven by severaldifferent factors. For example, retirement ofa transport aircraft could be determined bythe fatigue age of the airframe, the cost ofoperation, the availability of replacementparts, or the lack of logistic support for theengines. Therefore, corrosion would be onlyone of several possible factors taken intoaccount in making such a decision.

The costs attributable to corrosion willfall into two distinct categories, direct andindirect. Direct costs will be those associatedwith the detection, evaluation, repair andtesting of defects caused by corrosion.Direct costs can be considered as avoidable.Indirect costs would include the costassociated with building appropriatefacilities for accomplishing corrosionmaintenance, the cost of maintaining andconducting formal schools for the training ofcorrosion technicians, the cost in labor hoursfor annual training of corrosion maintenancetechnicians, and the cost to procure,distribute and install specialized equipmentin corrosion control shops. Indirect costs arenot directly accounted for and are thereforemuch more difficult to determine.

As to the purpose of this study,improvements in corrosion detectiontechnology could be expected to decreasedirect costs by:

• Decreasing the labor hours forinspection and repair of weaponssystems for corrosion

• Reducing the materiel requirements forcorrection of corrosion damage


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• Reducing unnecessary maintenancewhen it can be shown that suchmaintenance is not required [i.e.,structural tear down and destructivetesting]

• Reducing the training requirements andskill level required to perform adequatecorrosion maintenance

• and to decrease indirect costs by:

• Decreasing the down time of weaponssystems for corrosion maintenance

• Extending the service life of weaponssystems by improving the detection andcorrection of corrosion in its earlieststages

• Simplifying the training (both initial andperiodic) of corrosion specialists

• Improving corrosion maintenancepolicies to more accurately reflect theactual condition of each weapon system.

4.1Defense

Previous studies have estimated that thetotal cost of corrosion in the U.S. economyis on the order of 4 percent of GrossDomestic Product. Given that the U.S. has agreater than $7T (trillion) GDP, the impactof corrosion would be approximately $280B.These same studies identified total corrosioncosts in the Federal Government sector atabout $8B, or approximately 2 percent ofthe budget. Because the DoD has a higherproportion of equipment and facilities thanthe typical government agency, it would bereasonable to suggest that at least 3-4percent of the Defense budget is directly orindirectly influenced by the impact ofcorrosion on weapons systems, equipmentand facilities.

Defense costs also will be influenced bythe rate of replacement of weapons systems.Several weapons systems in the U.S. DoDinventory have an average age of more than30 years, while the average age of landvehicles in the civilian economy is much less.This would indicate that the proportion ofexpenditures needed to maintain older fleetsof vehicles is higher in the defensecommunity than it is in the civiliancommunity, and the cost impact of corrosionis correspondingly higher.

4.1.1 U.S. DefenseDue to the accounting practices in the

maintenance area, it is difficult to preciselydetermine costs of corrosion in defenseexpenditures. The data are not complete andmuch of the evidence is anecdotal in nature.However, certain trends are clear andinferences can be made. The U.S. defenseestablishment annually expendsapproximately $245B per year. If the defenseeconomy mirrors the overall economy ingeneral and corrosion costs are on the order of4 percent of the economy, then the total costof corrosion related activities in DoD wouldbe on the order of $10B, the avoidable costsrelated to corrosion would be approximately$2.5B per year.

Thi s est imate is s uppor ted b y oth ersou rces. A st udy s ponso red b y the Def ense Techn ical Infor matio n Cen ter(DT IC) a nd pu blish ed in Febr uary 1996cam e to a sim ilar concl usion . Thi s stu dy,tit led “ Corro sion in Do D Sys tems: Data Col lecti on an d Ana lysis (Pha se I) ,” st atedtha t “… the c ost e stima tes f or ex pense srel ated to co rrosi on wi thin the D oD al onecan reac h $10 B ann ually .” Th is st udyten ds to conf irm t he co nclus ion r eache dabo ve, t hat t he to tal c ost i mpact of


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cor rosio n to the D oD is on t he or der o f$10 B per year .

There have been bottom-up estimates gener ated by in dividual s ervices. A 1990study by the Ai r Force id entified c orrosionrelat ed costs, identified by weapon system,at ap proximatel y $718M pe r year. Th isamoun ts to abou t 1 percen t of the t otal AirForce budget fo r that yea r. Given t hat theArmy, Navy and the Marine Corps hav eequal ly severe corrosion problems, it wouldbe re asonable t o conclude that tota l DoDcosts would be approximat ely 3 time sthose of the Ai r Force, o r somewhat morethan $2B. This estimate i s consiste nt withthe “ top-down” estimate d escribed a bove.A rec ent update to the 19 90 Air For cestudy identifie s Fiscal Y ear 1997 c osts atappro ximately $ 795M.

The A ir Force C orrosion P rogramOffic e at the W arner-Robi ns Air Log isticsCente r periodic ally summa rizes theident ifiable co sts of cor rosion rel atedmaint enance wit hin the U. S. Air For ce. Fortheir purposes, corrosion maintenan ceinclu des all co rrosion tr eatment, a llpaint ing, all p rotective coating re moval andre-ap plication, washing, and inspec tion forcorro sion. Thei r data inc lude base levelmaint enance and depot lev el mainten ance.They note that 85 percent of the co sts areincur red at the depot lev el. The mo st recentstudy identifie d 1997 cos ts of

$794, 827,154. A similar a ssessment in1990 identified costs of $720,457,0 91. The1990 cost, esca lated by s tandard me thods,would be equiva lent to $8 58,784,857 in1997 dollars. T hat the 19 97 actual costs areless probably r eflect the downsizin g of thefleet that has occurred i n the inte rveningseven years as many older , highmaint enance cos t systems, such as t he F-4and m ost of the F-111s, h ave been r etired.Table 4.1, at t he top of the next c olumn,shows how the c osts due t o corrosio n aredistr ibuted.

Table 4-2 below provides examples ofthe costs attributable to corrosion forparticular weapon systems. These data arebased on a 1990 study sponsored by the AirForce Corrosion Program Office.

Element Total FY97 $ % of TotalRepair $ 572,352,704 72

Washing $ 28,443,783 4

Painting $ 145,951,530 18

AMARC $ 4,023,428 1

Vehicles $ 23,291,759 3

JCN ErrorCorrection

$ 1,207,137 <1

Munitions $ 6,247,341 <1

Metnav $ 13,309,471 2

Total $ 794,827,154 100

Table 4-1. U.S. Air Force Total Costs -FY97.


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Note that three systems, the B-52, the C-130 and the KC-135, account for 40 percentof the total of $720M described earlier. It isclear that corrosion costs are greater for largeraircraft and for older aircraft, as one wouldexpect. The reason for the relatively low costfor the B-1B is unclear. Examining the costchanges on a per aircraft basis between 1990and 1997 provides some interesting results,as seen in Table 4-3, which summarizes forthe same example set of aircraft.

Certain figures above stand out. It isilluminating to note that the costs per aircraftfor some, but not all, have increasedsubstantially. The reasons for this areprobably many. The basing of A-10 aircraftat western desert bases would decrease costs.Improvement of the cost accounting mayaccount for both positive and negativechanges. What is most clear, however, is thatthe cost per aircraft for most types, andespecially for large aircraft, has increaseddramatically in the past 7 years when thesestudies were conducted. The general trend, as

would be expected, is that as aircraft age, therelative cost of maintenance and repairattributable to corrosion increasessignificantly. In 1990, the average cost peraircraft was $62,611. In 1997, the averagecost was $104,872, an increase of 59 percent.These data suggest that corrosion costs peraircraft have been increasing at an averageannual rate of 6.8 percent, substantiallygreater than the overall rate of inflation.

Cor rosio n cos ts in the U.S. Navy(in cludi ng th e U.S . Mar ine C orps) are notas thoro ughly docu mente d. Ho wever ,cer tain studi es gi ve in teres ting insig hts i ntothe over all c ost i mpact of c orros ion f romsev eral diffe rent aspec ts. T he pr eviou slymen tione d DTI C stu dy in clude d the H-46 hel icopt er ai rcraf t as a cas e stu dy. A nnual

Table 4-2. Example U.S. Air Force Costsby Weapon System.

WeaponSystem

Total Cost($M - 1990)

Cost PerAircraft ($K)

A-10 Attack $ 21.5 $ 41.0

B-1 Bomber $ 1.1 $ 14.0

B-52 Bomber $ 80.3 $352.2

C-5 Transport $ 14.3 $136.0

C-130Transport

$115.7 $224.3

KC-135 Tanker $ 95.3 $147.9

C-141Transport

$ 57.6 $249.2

F-15 Fighter $ 19.6 $ 26.1

F-16 Fighter $ 14.3 $ 11.3

Table 4-3. Changes in Cost Per Aircraft, 1990-1997.

Weapon System Cost Per Aircraft(1990 $, K)

Cost Per Aircraft(1997 $, K)

Percent Change,1990 - 1997

A-10 Attack $ 41.0 $ 11.5 -72%

B-1 Bomber $ 14.0 $ 77.1 +451%

B-52 Bomber $352.2 $420.7 +19%

C-5 Transport $136.0 $830.1 +510%

C-130 Transport $224.3 $ 72.6 -68%

KC-135 Tanker $147.9 $341.5 +131%

C-141 Transport $249.2 $466.3 +87%

F-15 Fighter $ 26.1 $ 39.6 +52%

F-16 Fighter $ 11.3 $ 10.4 -8%

Fleet Average $ 66.1 $104.9 +59%


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cor rosio n cos ts we re di vided into dire ctcos ts an d saf ety c osts, a br eakou t not ava ilabl e els ewher e. Di rect costs for a fle etof 325 a irfra mes w ere i denti fied asapp roxim ately $135 M per year , or $420K per airc raft per y ear. This is su bstan tiall ymor e tha n the cost for any s ingle U.S. AirFor ce ty pe/fl eet o f air craft . Sin ce 19 80, t hesaf ety c osts of H- 46 mi shaps wher ecor rosio n was eith er a direc t cau se fa ctoror a pro bable caus e fac tor ( misha ps th atinc lude 11 fa talit ies, 7 los t air craft and 25dam aged aircr aft) total appr oxima tely$14 0M. W e not e her e tha t the aver age a geof the H -46 f leet is ov er 32 year s wit hpla ns to keep the aircr aft i n ser vice until the year 2015 .

US Army costs attributable to corrosionare also not well recorded. However, a 1986study undertaken by the U.S. ArmyMaterials Technology Laboratory, theresults of which appear in Table 4.4, isilluminating. This study examined thecorrosion-related costs from 1985 through1986 on the five-ton, 800-series truck, ofwhich 17,396 had been procured at thattime. The size of this fleet should be a goodindication of costs in similar ground vehicles.This study included the cost of downtime, acost element not considered elsewhere butreal nonetheless. The cost of downtime isreflected, at least in part, by the requirementto procure extra quantities of vehicles inorder to provide a minimum number ofcombat-ready vehicles at any one time. Thisis an example of the force structurediscussion earlier. This study found that theaverage cost per year for parts, labor,replacement and downtime for this fleet of

trucks was $7.8M. This amounted to $453per truck per year. These dollar figures are in1986 dollars.

These data are only for the U.S. Armyfleet of 5-ton trucks. When one considers allthe other land vehicles, aircraft and evenboats in the U.S. Army inventory, the costimpact of corrosion is much larger. Howmuch larger cannot be precisely determinedfrom the data currently available.

4.1.2 Canadian Defense CostsThe 1997 defense budget of Canada is

approximately $7.1B (US dollars). Using thesame heuristic as developed in paragraph 4.1above, the total cost impact of corrosion onthe Canadian defense budget would beapproximately $284M. The direct cost ofcorrosion related maintenance, repair andreplacement activities would be on the orderof $70M (USD). Using the same estimatingprocedure, the 1998 cost of corrosion-relatedactivities would be approximately $67M(USD), based on a slightly reduced budget.

4.1.3 Australian Defense CostsThe 1997 defense budget of Australia is

approximately $7.8B (US dollars). Using thesame heuristic as developed in paragraph 4.1above, the total cost impact of corrosion onthe Australian defense budget would beroughly $312M. The direct cost of corrosionrelated maintenance, repair and replacementactivities would be on the order of $78M(USD). Using the same estimating procedure,the 1998 cost of corrosion-related activitieswould be approximately $81M (USD) basedon a small increase in the budget.


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The Corrosion Prevention Centre ofAustralia, Inc. (CPC), cites a 1983 report(entitled “Corrosion in Australia: TheReport of the Australian National Centre forCorrosion Prevention and ControlFeasibility Study”) that concluded that theavoidable cost of corrosion in Australia was“around $2 Billion in 1982 A$.” The CPCalso estimates that the total cost of corrosionis about 3 times the avoidable cost. The CPCsuggests that an alternative estimate is thatthe total cost of corrosion is around 4percent of GNP. Based on a 1997 GDP of$405B, the total cost of corrosion to theAustralian economy would be on the orderof $16B while the avoidable costs would beapproximately $4B. Applying that sameproportion to the Australian Defence Budgetyields a direct cost of corrosion (to thedefense establishment) of approximately$78M.

4.1.4 Summary

Combined, the defense establishments ofthe three NATIBO sponsor countriesexpend on the order of $2.1B per year oncorrosion related activities and equipment.These costs could be reduced with betterNDE/NDI and corrosion detectiontechnology, and productivity improvementsin the maintenance areas. The magnitude ofthese expenditures would make the area ofcorrosion detection, characterization, and

prevention a tempting target for futureR&D.

4.2Commercial

It has been estimated that corrosion ofmetals costs the United States economyalmost $300B per year. Approximately one-third of these costs could be reduced bybroader application of corrosion resistantmaterials and the application of bestcorrosion-related technical practices. Asmaller but not insubstantial portion wouldbe impacted by the application of improvedcorrosion detection technologies.

The original study by Batelle, based onan elaborate model of more than 130economic sectors, found that in 1975,metallic corrosion cost the U.S. $82B, or 4.9percent of its Gross National Product. Itwas also found that 60 percent of that costwas unavoidable. The remaining $33B (40percent) was incurred by failure to use thebest practices then known. These were

referred to asavoidable costs.

In a 1995update to theoriginal study, thepanel estimatedthat avoidablecorrosion costs

were now 35 percent of the total of nearly$300B but still accounted for over $100Bper year. This figure represents a cost to theeconomy that may be reduced by a broaderapplication of corrosion-resistant materials,improvements in corrosion preventionpractices, and benefits from investment incorrosion related research.

The commercial sector costs of corrosionare particularly relevant to this study. For

Table 4-4. Total Corrosion Costs, U.S. Army 800-SeriesTrucks.

Year Parts/Labor/Downtime Per Truck

Estimated Numberof 5-ton Trucks

Total

1986 $ 381.37 47,000 $ 17,924,390

1985 $ 367.77 47,000 $ 17,285,190


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example, these costs include a tremendousamount of national infrastructure in roads,bridges, and utility systems managed byliterally thousands of governments andcorporations. Costs and investments on thepurely commercial side will have cleareconomic incentives. Costs and investmentson the governmental side will have the addedcomplexity of political and tax revenueimplications.

4.3Summary

The cost impact of corrosion issubstantial and difficult to quantify. Thecosts that can be avoided by the deploymentof improved corrosion detection technologycannot be precisely determined but are asignificant portion of the total. While cost isa major factor in making decisions regardinginvestments in the corrosion detectiontechnology area, other factors bear on thesedecisions as well. These factors include theconfidence level in the safety andeffectiveness of mission critical systems andthose components in which their failurecould cause serious injury or loss of life.

Improved corrosion detection couldincrease maintenance costs earlier on in thelife cycle of a system, but in all likelihoodwould contribute to the reduced life cyclecost of maintaining the system in missionreadiness state in the course of its servicelife. Currently, some amount of corrosiondamage in weapons systems goesundetected. If better or broader applicationof technology finds more corrosion earlieron, then corrosion control and preventionmeasures can be deployed at that stage.Thus, more extensive corrosion damagewould be avoided and the extension ofservice life of a system could be realized.Other positives associated with such an

increase would include a higher degree ofconfidence in the structural integrity (andtherefore safety, reliability and longer usefullife) of fielded systems.

As the force structure ages (i.e., theaverage age of fielded systems, howevermeasured), the question becomes one ofinvestment in technologies, equipment,facilities, training and personnel that willhelp to assure that the force structureremains militarily effective. In many cases,the option to replace entire items does notexist. We cannot replace a retired aircraftwith new production if that system is nolonger in production. In this instance,extraordinary investment may be required tokeep the system in the active inventorywhile replacement systems are developedand deployed.

While the annual cost of corrosion isinteresting, the more relevant question wouldbe, “What is the appropriate level of futureinvestment in corrosion detection technologyto help assure the future safety andreliability of the planned operational forcestructure?” This question should beanswered in the form of bottom-up budgetrequests generated by the logisticscommunities of the individual Services inlight of established military requirements tofield safe and effective systems for someprescribed period of time. More specificallyfor the purposes of this NATIBO-sponsored study, the question becomes:“What corrosion detection technology couldbe advanced in the near term that would havea significant impact on reducing the impactof corrosion on military and commercialsystems?”


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5. Corrosion DetectionTechnologies Research andApplication Activities

5.1Introduction

The following sections describe some ofthe corrosion detection technology researchand application activities going on within theU.S., Canadian and Australian defense sectoras well as within other governmentorganizations. Commercial sector activitiesand academic institution activities are alsodocumented. This list is not intended to beall-inclusive but provide a snapshot of someof the major developments that areoccurring.

5.2Defense Sponsored Activities

The military is considered the primarycorrosion detection technology driver. Thisis due in part to the fact that militarysystems typically are fielded longer, havehigher cycle rates and operate in morecorrosive environments than commercialsystems. And with the continual decline indefense spending, the service life for defensesystems will be extended even longer with aconsequent focus on reducing maintenancecosts for these existing systems.

5.2.1 U.S. ActivitiesCorrosion is considered to be the number

one cost driver in life cycle costs of DoDweapon systems. Throughout the DoD,corrosion is regarded as less of a safety ortechnical issue but rather more of aneconomic issue. This is because thecorrosion problems encountered by themilitary in their defense systems has beendetected and repaired before it could becomea safety problem. Currently, corrosionprevention is a higher priority within themilitary sector.

Technology has been identified as one ofthe primary mean of reducing the impact ofcorrosion on DoD weapon systems. Oneway is to implement more corrosionresistant materials into the defense systems.This could be accomplished by makingmaterials more corrosion resistant by usingcorrosion inhibitors, surface treatments, andcoatings. Implementing a decision making aidwould also be useful and provide asystematic way to model the long-termcorrosion performance of various materialsand structures in order to determine theoptimal corrosion prevention and controlprogram for new weapon systems during theacquisition cycle and throughout the servicelife of the system.

The other way in which technologycould be employed to combat the effects ofcorrosion in systems is to aid maintenancepersonnel in locating corrosion sites andproviding them with optimal solutions tocorrecting the problems. The DoD S&Tcommunity is researching a number ofdifferent technologies to achieve these goals.

5.2.1.1 U.S. Air ForceLike the other Services, the Air Fo rce

budge t to build new defen se systems hasbeen reduced an d, in resp onse, the AirForce is lookin g for ways to extend theservi ce life of their exi sting airc raft in or derto me et mission demands. The U.S. A irForce has many old (20 to 35+ years )aircr aft that a re the bac kbone of t he totalopera tional for ce. All of these old er aircraf thave encountere d, or can be expecte d toencou nter, agin g problems such as f atiguecrack ing, stres s corrosio n cracking ,corro sion, and wear. Exte nding the servicelife and use of these air craft has resulted i nincre ased maint enance and repair co sts due


38

to st ructural c racking an d corrosio nprobl ems.

In the late 1950s, the Air Force startedto develop an engineering process forsystematically controlling the causes offatigue failure of its aircraft structure. Theprocess was institutionalized as the aircraftstructural integrity program (ASIP) in 1958.As a result of a F-111 accident and C-5Awing cracking problems in the late 1960s andearly 1970s, the Air Force’s ASIP processwas extensively modified. Changes were putinto effect to control aircraft fatigue cracking,by requiring systematic damage toleranceassessments, whereby the designs accountfor the presence of preexisting cracks. Thedesign assumed that flaws, defects, andmaterial anomalies could be present at thetime of manufacturing and/or immediatelyafter in-service inspections, and that if thesecracks grew, these cracks would never reacha size which would jeopardize aircraftsafety. The ASIP process ensures thatfatigue cracking is controlled throughout theoperational life of the aircraft.

In the Air Force, each aircraft (weaponsystem) has a force structural managementplan (FSMP), which was required as part ofthe ASIP process. The aircraft’s FSMP wasbased on a durability and damage tolerantassessment (DADTA) of the airframesubjected to anticipated operational serviceand anticipated damage scenarios. This planguides the inspection, assessment, repair,and maintenance of the airframe according tohow the aircraft is being operated. Between1975 and 1990, the Air Force spentapproximately 1 million man hoursconducting DADTAs on its aircraft andupdating their FSMPs. Updating the FSMPreestablishes the remaining service life of thestructure (in terms of expected operations)

and forecasts the expected structuralmaintenance costs associated with thisservice life goal. It is the responsibility ofthe major operating commands(MAJCOMs) and aircraft weapon systemprogram office (SPO) to manage this part ofthe process.

Through the Aircraft Structural IntegrityProgram and through durability and damagetolerance assessments of older aircraft, theAir Force has identified many potentialproblems and developed individual trackingprograms and structural maintenance plans.However, most of the effects of corrosionare not reflected in aircraft structuralintegrity models, even though corrosion isone of the most costly maintenanceproblems for Air Force aging aircraft.

The Air Force’s R&D community isresponsible for supporting this engineeringand management process by improving thetechnology products and delivering these in aform which facilitates their application bythe sustainment community user. One suchR&D product being researched is aninexpensive, user-friendly nondestructiveinspection system which has wide rangingcapability for detecting subsurface (hidden)cracking or corrosion damage.

Extensive interactions between the AirForce R&D and sustainment communitiesare required to establish the class ofsustainment problems which are causingsafety and economic concerns. Astechnology products are defined in responseto these needs, the R&D community isworking together with the users inestablishing the specific requirements foracceptance by the sustainment community.

Military fleet operators have traditionallydepended on corrosion prevention as a means


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of dealing with potential corrosion problems.However, the Air Force, faced with the realityof extended life requirements for their aircraft,is finding significant levels of hidden corrosion.Also, the extent of corrosion damage amongsimilar aircraft can vary widely, due to thedifferent environmental exposure the aircrafthave been subjected to and the level and typeof maintenance that the aircraft have received.The Air Force is actively researching the beststrategy for mitigating the effects of hidden(and possibly widespread) corrosion on thecontinuing safe operating life of their aircraft.

One of the Air Force’s primary R&Dgoals is to reduce operations and maintenancecosts of Air Force weapons via enhancedNDI/E technology. The USAF is consideredto have the largest corrosion detectiontechnology development program among thethree Services. For over 25 years, the AirForce has maintained a formal fleetwideNDE/I monitoring program as part of itsAircraft Structural Integrity Program (ASIP).The established Air Force NDE/I research anddevelopment program is coordinated withboth the Air Force System Program Offices(SPO) and ALC technology personnel andaerospace industry technology representativesin order to help assure that capabilities matchrequirements to the extent possible.

At present, the Air Force relies primarilyon visual inspection techniques to uncovercorrosion damage. Eddy current (EC) andultrasonic (UT) methods are the main meansused in current practice to detect small cracksnondestructively in aircraft structuralmembers, with radiographic (RT), fluorescentliquid penetrant (FPI) and magnetic particle(MP) methods being employed for morespecialized inspections. However, the AirForce believes there remain a number ofNDE/I technology improvements needed to

keep pace with continually advancingmilitary mission/commercial flight operationsand vehicle technology changes. Two damagescenarios indigenous to aging aircraft requiresignificant NDE/I advances in the near term:(a) hidden corrosion detection, imaging andcharacterization and (b) widespread fatiguedamage/cracking detection and quantification.Another key logistics need cited by the AirForce is rapid NDI for advanced compositeswith complex shapes and densities. The AirForce is looking to improve existingtechnologies and to develop new technologiesto detect these potential failure-causingdefects.

5.2.1.1.1 Air Force Office of ScientificResearch

The Air Force Office of ScientificResearch (AFOSR) manages the Air Force’sbasic research program. AFOSR initiated aprogram in the early 1990s in the area ofdetection and prevention of corrosion inaging aircraft. Their objectives were to:

• Develop a science base necessary forpractical NDE instruments capable ofdetecting hidden corrosion with highaccuracy, sensitivity and versatility

• Understand the fundamentalchemistry of corrosion

• Develop models of corrosioninitiation and propagation

• Develop mathematical models ofimpedance imaging, and

• Perform controlled experimentswhich determine the effect of selectedparameters on the corrosion process.

The AFOSR funded a number ofUniversity Research Initiatives in this area,including the following:


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• Iowa State University -Nondestructive detection andcharacterization of corrosion in aircraft.Their objectives were to develop pulsededdy-current methods to detect hiddencorrosion at joints in the skins oftransport aircraft and develop energy-resolved x-ray techniques for complexcomposite structures in high-performance aircraft.

• Lehigh University - Corrosion andfatigue of aluminum alloys: chemistry,micromechanics and reliability. Theirgoals were to develop a basic mechanisticunderstanding of material degradationprocesses and formulate mechanistically-based probability models for reliabilityassessments.

• SUNY at Stony Brook - NDE ofcorrosion and fatigue by laser specklesensor and laser moiré. They were taskedto perform basic research that would leadto the development of two new NDEtools for the detection of corrosion-baseddegradation.

• University of Chicago - Scanningtunneling microscopy studies of themorphology and kinetic pathways ofcorrosion reactions of stressed materials.Their role was to develop anunderstanding of materials corrosion,with emphasis on the role of surfacechemical reactions and atomic-levelmicrostructures, and to study the effectof stress on reactivity of materials andthe role of surface defects on oxidationreactions.

• University of Connecticut -Experimental and theoretical aspects ofcorrosion detection and prevention. Theuniversity’s objectives were to

investigate initiation and growth kineticsof corrosion using electrochemicalimpedance spectroscopy and study x-ray computed tomography for NDE.

• University of Delaware - NDE ofcorrosion-damaged structures. Theuniversity applied the electricalimpedance tomography to corrosiondetection and monitoring.

• Vanderbilt University - Frettingcorrosion in airframe riveted and pinnedconnections. They assessed thecontribution of fretting to the corrosivedeterioration of riveted and pinnedconnections.

• Wayne State University - ThermalWave Imaging for NDE of hiddencorrosion in aircraft components. WayneState developed thermal wave IR NDEinstrumentation capable of detectinghidden corrosion.

Most of these efforts have beencompleted and new programs were started inFY 97 as part of the Third MillenniumInitiative. These new programs includeinvestigating development of pittingcorrosion in aluminum alloys, performingfundamental research to characterize andanalyze widespread fatigue damage, andinvestigating and demonstrating innovativeNDE/I techniques that have the potential toproduce significantly higher defect detectionand characterization accuracy and reliabilityfor detection of corrosion and small fatiguecracks.

5.2.1.1.2 USAF Wright LaboratoryMaterials Directorate, Wright-Patterson AFB

The USAF Wright Laboratory managesthe Air Force’s applied research and


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advanced development program in manyaeronautical-related technologies. The AirForce’s R&D thrust supporting thestructural integrity program is to determinethe impact of corrosion damage on theintegrity of an airframe. The researchscientists noted that, unfortunately,corrosion takes many forms that couldimpact structural integrity in different ways.And for each form of corrosion damage(uniform, exfoliation, pitting, crevice,intergranular, stress corrosion cracking, etc.),a structural model of the corrosion damageneeds to be created to accurately assess itseffect on fatigue life and/or residual strength.

In most cases, structural models describethe effect of geometric changes caused by thecorrosion, and the structural engineer caneasily evaluate the effects. But in somecases, corrosion can substantially lower thestructure’s resistance to the development ofnew cracks, and this effect is not alwayseasy to accurately model. For many of theolder aircraft, being able to anticipate thedevelopment of maintenance causing eventswith some degree of certainty is a majorrequirement for the system program offices.The problem with stress corrosion crackingof the thicker components manufacturedfrom older 7000 series aluminum alloys hasbeen a pervasive hidden corrosion problem,causing unanticipated major expenses andsubstantial downtime for aircraft in depotmaintenance due to limited spares stocked.

Wright Lab representatives stated thatthe Air Force’s research and developmentefforts support: (1) developing what theupper limits of corrosion damage can bebefore this damage leads to a safety problem,(2) developing structural metrics forcorrosion that are used to measure the ratesof corrosion for specific types of corrosion

damage, and (3) providing a tool set that canbe used, in conjunction with the parallelNDE work, to determine maintenancestrategies for dealing with corrosion presentin the airframe.

The researchers pointed out that highlycapable nondestructive evaluation andinspection (NDE/I) methodologies andprocesses are an enabling tool in the lifecycle management of aircraft systems fordetection and characterization of defects,flaws or anomalies. They contended that,while the current state-of-the-art portrayssignificant advances in recent years, majorcapability improvements still must follow inorder to satisfy operational requirements.


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Their goals in regard to this encompass:

1. Developing advanced nondestructiveevaluation/inspection (NDE/I) systemsand methodologies for aging aircraftwhich have the following characteristics:

• Improved sensitivity fordetecting damage

- Hidden corrosion damage such as in structural interfaces, including around fastener holes

- Cracking damage such as small, tight cracks and multiple cracking

• Accur acy (imp rovedPOD/C L) - small er margins of error, repea table and consistent equipment (thro ugh design improveme nts,bette r calibrat ion capabi lities, et c.)resul ting in lo wer false call rates ,less required o perator in tervention ,maxim ized Proba bility ofDetec tion/Confi dence Leve ls

• Speed of application - fastersetup and scan rates withoutsignificant loss of fidelity, optimumautomation, optimumportability/maneuverability, optimumruggedness

• Data flow manag ement -high rate, high fidelity dataacqui sition, an d processi ng, datafusio n, interpr etative an alysis and archi ving capab ilities

• Operator interfaces -optimized for ease of handling,controlling, instructing,interpretation; optimumincorporation of automation

• Equ ipmen t ver satil ity fo rdet ectin g mul tiple dama ge ty pes -

emp hasis on d evelo ping/ desig ningmul tifun ction NDE/ I sys tems(ex empli fied by th e AF MAUS IIIult rason ic-ed dy cu rrent scan ningsys tem) to fa cilit ate e ffici entins pecti on mo dalit y cha ngeov ers,red uce i ndivi dual item inven torie s,yie ld gr eater cost bene fits andope ratin g eff icien cies

• Reduced

- System cost and cost of operation(overall cost of inspection)

- System complexity

- System size and weight

• Validated/demonstrated inaircraft environment

2. Increasing Modularity of NDI Systems

• Develop NDE/I systemswhich have efficient modularelements for maximizing andstandardizing common features suchas:

- Image enhancement and display

- Data fusion and data archival

- Diagnostics and interfaces withdiagnostic tools

- Sensor technologies

- Automation/motion control

3. Reducing the Cost to Inspect Aircraft

• Systematically reduce thecost of inspections by focusing on

- Economical inspection processessuch as more efficient scan plans,interactive process diagnostics,


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modular system maintenanceprocedures

- Enhanced training for inspectors

- Simplified and standardizedcalibration procedures

- Minimization of repeat inspections through increased detection sensitivity and reproducibility features

- Evolving of more affordableNDE/I processes ( i.e., filmlessradiography)

- Accelerated systemdemonstration and validationprocesses.

The Air Force’s R&D strategy is to havenondestructive evaluation/inspectionmethodologies and procedures that providereliable defect/flaw/damage detection withthe maximum affordable sensitivity,accuracy and speed to support Air Forcemissions. The current aging aircraft-relatedNDE/I R&D program focusing on improveddetection of hidden corrosion and smallcracks is planned to produce, demonstrateand transition required advancements tomeet specific Air Force customer-identifiedneeds.

This program also has connectivity withgermane FAA and NASA efforts so as tomaximize technology developmentcoordination and transfer.

Their goal is to have NDE/I that not onlysupports fleet management and airworthinessassurance programs but also providesessential detection capability data tostructural integrity methodologies thatpredict structural life and determine structural

maintenance, inspection and repairrequirements, schedules and cost as well asevaluate maintenance and repair strategies.The current aging aircraft-related NDE/I R&Dprogram focuses on detection/characterizationof cracks smaller than those that would leadto the onset of widespread fatigue damage(WFD), when multi-site and multi-elementdamage (MSD and MED) scenarios exist, and2) detection/characterization of hiddencorrosion prior to reaching the maximumlimits set by structural integrity as well aseconomic models.

To achieve these goals, the Air Forceintends to make maximum use out of newinnovations and advances in sensor, imaging,image enhancement, simulation, model-baseddefect/flaw/damage signal processing anddecision, and ultrahigh rate data managementtechnologies from all fields of science. Whereappropriate, they will emphasizeincorporation of modular NDE/I process andsystem elements in new/improved designs inorder to optimizeversatility/interchangeability andmaintainability/supportability; increasestandardization of equipment, procedures,calibration, etc.; and reduce acquisition andoperating costs. Demonstrations andvalidations of new technology developmentswill be conducted, as appropriate, in aircraftmaintenance/testing settings andenvironments in order to duplicateoperational conditions to the maximumextent possible. These will include AirLogistic Centers, commercial operator beta-site test locations, the FAA AirworthinessAssurance Nondestructive InspectionValidation Center (AANC) and availableOEM facilities.

Currently, Air Force programs areemphasizing low frequency EC process


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development for interior layer cracks (thelower the frequency, the deeper thepenetration) since the electromagnetic fieldsare much less affected by interfaces (such asin lap joints and stack-ups) than areultrasonic signals. The Air Force considershigher sensitivity EC probe designs, refinedsignal processing and more rapid scanningmethods and equipment key improvementareas.

The detection of hidden corrosion inaircraft structures with standard NDE/Imethods has been investigated by all agenciesfor a number of years with historicallylimited success. Recently, increased emphasishas and is being placed on the more promisingof the investigated methods such as improvedultrasonic, eddy current, thermographic, andoptical techniques; specialized digital x-ray(RT); and development and demonstration ofin-situ embedded sensors (e.g., optical fibers,galvanic bi-metallic), etc. In addition, the useof EC with improved imaging capabilities isbeing studied for applicability. Meanwhile,new fundamental investigations areunderway/planned by the Air Force to againseek/identify other potential corrosiondetection/characterization methodologies thatmay apply. Related work is ongoing to moreprecisely and quantitatively define corrosiondamage areas to help refine nondestructivedetection and imaging processes and to trackcorrosion progression rates nondestructively,thereby providing essential data for lifeprediction models. Studies will continue toseek new/modified NDE/I methods that yieldreliable signals from very early stagedefects/flaws and that also provide morefinely resolved larger flaws.

The Air Force’s goal is to optimizeNDE/I processes for speed and minimizedcosts in order to meet operational schedules

and budgets. Their future plans includestudying advanced intelligent sensortechnology (both military and commercial),selected and integrated into state of the artNDE/I instrumentation designs and interfaceswith limited access inspection sites to yieldsignificantly increased detection accuracy,sensitivity and consistency. Concentrationwill be placed on detection of nascentdefects/flaws to produce reliable data tosupport more accurate structural integrityassessments. Studies will continue to seeknew/modified NDE/I methods that yieldsignals from very early stage defects/flawsand that also provide more finely resolvedlarger flaws. Advances in probability ofdetection (POD) determination models andmethodologies will be developed,demonstrated and validated using accurate,validated aircraft inspection data to yieldmore precise estimates of structural damagegrowth rates, life estimates and maintenancestrategies.

The Air Force intends to develop faster,more robust NDE/I data acquisition, model-based analysis, signal and decisionprocessing and archiving from new state-of-the-art, human computer interfacetechniques, data management advances, andthe like, to support significantly fasterinspection processes. Advanced automationand motion control technology will becoupled optimally to higher accuracy state-of-the-art NDE/I systems targeted toproduce high inspection scanning rates overlarge structures capable of a higherdefect/flaw/ damage detection (POD) ratethat is cost effective.

Integ ration of advanced N DE/Iproce sses into a Conditio n BasedMaint enance (CB M) system prototypewill be develop ed and dem onstrated


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compr ehensively , includin g definiti on of theeffec ts, limits and poten tial of th e keycompo nents of t he inspect ion proces s onsyste m optimiza tion and P OD. State- of-the-a rt visuali zation tec hnology,exemp lified by that from virtual re alitydevel opments, w ill be stu died to ev aluatethe p otential o f applicat ions to th e designand r efinement of advance d NDE/Iproce sses and t echniques and NDE/Iopera tor traini ng and to measure th e effecton ND E/I POD. T hey also i ntend to f ocuson ad vanced dev elopment o f accurate ,relia ble, minim um-cost ND E/I proces s andinstr ument/equi pment desi gns, throu gh theadapt ation and applicatio n of state of theart v irtual pro totyping t echnology, withopera ting prope rties that promote h ighPOD l evels.

In an effort to reduce operation cost (anestimated savings of over $1M per year) andreduce hazardous chemical handling anddisposal costs at Air Force Air LogisticsCenters and field depots, Wright Laboratoryhas initiated a research effort into replacingtheir conventional X-ray inspection methodswith filmless radiography for aerospaceapplications. This effort is evaluating thefeasibility of using a filmless radiographysystem with digital storage capability foraerospace structures and transitioning it toAir Logistics Centers.

5.2.1.1.3 U.S. Air Force CorrosionProgram Office, Warner Robins AFB

The C orrosion P rogram Off ice is asubdi vision of the Air Fo rce Air Ma terielComma nd. The of fice was c reated for thepurpo se of ensu ring that the Air Fo rce hasa via ble progra m to preve nt, detect , andcontr ol corrosi on and min imize the impactof co rrosion on Air Force systems ( Air

Force Instructi on 21-105) . Otherrespo nsibilitie s include extending theservi ce life of Air Force systems a ndimpac ting the a cquisition process f or newAir F orce syste ms.

The office was established in 1969 withthe publication of Air Force Regulation 400-44. This program was centered at the AirMaterial Area in Mobile. When the AirMaterial Area in Mobile was closed, theoffice was moved to Warner Robins AirMaterial Area in Georgia. The first annualCorrosion Managers’ Conference was held in1969, and the first Corrosion Summary wasissued in February 1972. In October 1979,Warner Robins Air Logistics Center(WRALC) was officially tasked withmanaging the Air Force Corrosion Program.In October of 1995, the Corrosion ProgramOffice was organizationally realigned as anoperating location under Wright Laboratories.The Office consists of both civilian andmilitary personnel as well as specialized labsfor corrosion research.

Specific engineering functionsaccomplished by this office are tri-servicetechnical liaison/support, technologyinsertion, new technology demonstration/validation at ALC/field units,engineering/technical consultation andcorrosion prevention and control policyestablishment. Activities of the Air ForceCorrosion Program Office include thefollowing:

• New Materials and ProcessesTechnology Insertion Projects

• Corrosion effects on aging aircraft

• Cost of Corrosion Study

• Aircraft Depaint/Cleaning Projects

• New Weapon Systems Support


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• Classified Systems Support

• Thermoplastic Power

• Coatings

• Metal Arc Spraying

• Avionics Corrosion

• Hazardous Waste Reduction/NASA/DOD/ EPA

• Corrosion Training and Education

• Materials Evaluation.

The Corrosion Program Office isseparate and distinct from the NDI ProgramOffice at Kelly AFB in San Antonio, TXand the Aging Aircraft Program Office atWright-Patterson AFB, though they docoordinate on issues of common interest.

An important corrosion issue raised bythe Corrosion Program Office engineers andtechnicians group was that 90 percent ofcorrosion prevention is applied on the outersurfaces of aircraft, as opposed to the morestructurally important interior of the aircraft.One preventive measure implemented as aresult of Corrosion Program Office analysishas been the application of a glossy whitepolyurethane coating underneath all latrinesand galleys. Another issue raised by thegroup was the inconsistent use of sealantsby OEMs on rivet joints.

5.2.1.1.4 Aging Aircraft Office

The Aging Aircraft Program Office wasestablished by the Air Force MaterielCommand in 1996 to transition technologiesfrom laboratory research and commercialtechnology development to the Air LogisticsCenters that will address the needs of agingaircraft. The mission of the Aging AircraftProgram Office is to work within and

outside the Air Force to transitiontechnologies that will extend the lives andreduce the costs of operating and maintainingaging aircraft systems. The program istargeted towards maintaining airframeintegrity and emphasizes developing cross-cutting solutions that will benefit multipleaging aircraft systems. The projects fundedby this program will address critical needs ofthe aging fleet such as corrosion, structuralintegrity and improved non-destructiveinspection techniques. As an agent fortechnology transition, the program officeserves as a link between the R&Dcommunity and the sustainment community.

The program office sponsoredseveral projects in FY97, utilizing fundsprovided by HQ AMC and HQ AFMC,that were geared towards hidden corrosiondetection. One project made someimprovements to the D-Sight system andvalidated the improved system. D-Sight,which utilizes a dual pass light reflectionmethod, is of particular interest forinspecting lap joints. Another project isevaluating, improving, and validating a C-scan eddy current system (Zetec MIZ 22coupled with the Krautkramer BransonANDSCAN). The final FY97 projectinvolved improving and evaluating theMobile Automated Scanner (MAUS)system, which can be used for a variety ofinspections including disbonds,delaminations and corrosion detection. Oneof the significant improvements made to theMAUS system was a movable track systemto semi-automate the inspection process.

In FY98, the program office will befunding some additional work on the D-Sightsystem, as well as a new effort to evaluatethermography and dripless bubbler


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technologies as means to detect hiddencorrosion in the vicinity of wing skinfasteners.

5.2.1.1.5 Sacramento Air LogisticsCenter, McClellan AFB

McClellan employs the followingcorrosion detection technologies in theirinspection of defense systems, primarilyaircraft:

• Ultrasonics

• N-ray

• X-ray

• Eddy current

• Magnetic particle

• Laser ultrasonics.

McClellan AFB has two neutronradiography systems. One is stationary,designed to do component parts within fourbays. The second is a maneuverable systemdesigned to inspect components while stillattached to the aircraft.

At the heart of the state-of-the-artstationary neutron radiography system isthe newest research reactor in the U.S. Thefacility was developed to detect low levelcorrosion and hidden defects in aircraftstructures using neutron radiography. Theradiography system can accommodate partsto 34 feel long, 12 feet high and up to 6000pounds in weight. The center’s datasystems are designed to provide on-line andoff-line tracking of critical components anddata reduction for trend analysis. Filmradiography systems are also available whichcan detect extremely low levels of hydrogenand surface corrosion. The facility’s realtime radiography system has the capabilityto image dynamic events such as data for

egress and hydraulic systems, explosivecharges, and oil fill levels, respectively.

The maneuverable N-ray systemconsists of a hangar enclosed gantry robotwith a work envelope of 84 feet wide by 85feet diameter by 25 feet high. It is the onlyone of its size in the world, capable ofscanning an entire aircraft. The six-axisrobot is capable of moving the neutronsource along a preprogrammed inspectionpath to inspect the entire aircraft once it ispositioned in the hangar. This method ofinspection is capable of detecting moisture inareas where normal inspection methodswould fail without extensive disassemble.

The inspector controls the operationfrom a remote control station and can stopthe inspection process at any time toperform specific functions such as zoom andsearch of a selected location. If interrupted,the system is capable of picking up theprevious inspection point within a .025 inchradius.

The following aircraft have used thissystem: F-111, F-15, the Navy’s F-14Tomcat, the Army’s AH-64 ApacheHelicopter, the Canadian CF-18, and theAustralian F-111C and G models.

McClellan also has a maneuverable,real-time x-ray system which improvesperformance of x-ray of composite materialsin assembled aircraft while providinginformation not available from otherinspection processes. The system supportsreal-time x-ray aircraft inspection using arobot-mounted system. The system is 77feet wide be 90 feet diameter and 25 feethigh, and has a 420 kV and 160 kV x-raysystem mounted on a large gantry robotwhich is installed in a specially constructed,shielded aircraft hangar. This system is used


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to check wings and other structuralcomponents for fatigue cracks, internaldamage to hinges, and frame members.Bonded honeycomb components are checkedfor core damage and water/corrosion.Outputs from this x-ray inspection systeminclude structural and bonded integrity-defect data, photovideotape graphs recordeddata, corrosion-moisture detection location,and crack-debond detection and location. ACanadian CF-18 was sent to the ALC for afull N-ray and X-ray evaluation in 1996.

5.2.1.1.6 Oklahoma City Air LogisticsCenter, Tinker AFB

The Oklahoma City Air Logistics Centeris researching existing and emergingNDE/NDT techniques for aging aircraftthrough its CORAL REACH program. Inconjunction with ARINC and Boeing, theresearchers have invasively disassembled acomplete KC-135 aircraft. The corrosionfound on all structural members wasdocumented. In the course of thisinvestigation, the researchers foundcorrosion in many areas that are hiddenand/or inaccessible even during depotoverhaul and therefore are missed by currentvisual inspection.

As a result of this project, theresearchers embarked on an effort toevaluate, prototype and transition state-of-the art NDI systems to C/KC-135 PDM forhidden corrosion detection in fuselage lapjoints and around wing skin fasteners. Theyhave completed four comprehensiveevaluations of commercial off-the-shelfequipment. No equipment was foundsuitable to detect intergranular corrosionaround wing skin fasteners. The group iscurrently studying NDI equipment thatwould detect corrosion around these wing

skin fasteners and is in the process oftransitioning the MAUS III /IV technologyinto their inspection procedures.

The ALC is also working with Boeing,ALCOA, the University of Utah, andWright Labs to determine fatigue crackgrowth rates in lab grown corroded C/KC-135 structural materials. The resultingfatigue crack growth data will be used inC/KC-135 structural life assessments toaccount for corrosion effects. To date, testswere completed on 2024-T3/T4 and 7075-T6 material with light to moderate corrosion.These tests showed some increase in crackgrowth rate compared to uncorroded, but theteam believes extensive tests with specimensexhibiting more severe corrosion are needed.

They have conducted fatigue testing andanalysis of C/KC-135 fuselage lap joints andupper wing skin panels with precorrosion inorder to use the resulting fatigue life data as agross estimate of the effects of corrosion onfatigue life. In addition, the ALC is involvedin corrosion growth rate studies to determinehow fast corrosion grows on/in C/KC-135aircraft structure at different geographicaloperating locations.

The ALC is also in the process ofevaluating the effectiveness of externallyapplied corrosion preventioncompounds/inhibitors in reducing oreliminating corrosion on C/KC-135 aircraft.This work is being done in conjunction withWright Labs and UDRI. If some of thesecorrosion preventative measures provefeasible, field applications and exposureevaluations will be made.

The researchers are working with NASALangley and Wright Labs to determine theeffects of active corrosion, prior corrosiondamage, corrosion by-products and corrosive


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environments on fatigue crack nucleation andfatigue crack growth rate of C/KC-135structural materials.

Together with the FAA, they areconducting full-scale testing of C/KC-135/707 generic fuselage panels with naturalprior corrosion damage in hidden andinaccessible areas to determine theinteractions between corrosion and fatigueand the effects on structural life.

In conjunction with the University ofOklahoma, the ALC is going to conducttesting and analysis of the C/KC-135structural components with prior corrosion.They want to compare this data withprevious results of uncorroded and labgrown corroded specimens.

They have completed work on acorrosion characterization and comparisonmapping project, providing a visualrepresentation of the location and severity ofcorrosion found during aircraft disassemblyand inspection overlaid with existing ASIPpoints. This data will help identify locationswith potential fatigue-corrosion interaction.

The ALC has also finished testing andanalysis of precorroded C/KC-135 structuralmaterials to determine the static strength andfracture toughness compared to uncorrodedmaterials.

Currently underway is work with Boeingto conduct corrosion fatigue crack growthtesting in a corrosion environment to helpdetermine the effects of such environmentson fatigue crack growth. They are alsoworking jointly to test pre-corroded fastenerhole multi site damage in an attempt to gaugepre-corroded fatigue crack growth andresidual strength of KC-135 aircraftmaterials with fastener holes. In addition,they are working together on designing,

developing, and building a prototype of theStratotanker Condition Analysis andLogistics Evaluation (SCALE) systemengineering tool. The system will be able tocollect, document and analyze KC-135corrosion discrepancies/information for allthe structure by tail number and for theentire fleet. It will include graphicallyenhanced displays, logical and physicalmodels, data entries by input, scans, digitalphotos and NDI output.

5.2.1.2 U.S. NavyThe Navy has the largest monetary

investment in corrosion research. They arealso considered to have the best corrosionmaintenance and training practices.

Naval systems encounter a wide range ofcorrosion problems. In trying to fix thesecorrosion problems, the Navy needs toovercome some unique hurdles due to thesevere environment and lack of conveniencesthat are available to land-based systems.These include dealing with limitedmaintenance capability and space, theinability to wash their aircraft as frequentlyas needed, and the lack of contractor supportfor rework during deployment.

The Navy is focused on three generalapplication areas: ships/submarines;aircraft/weapons; and general corrosion. Thehighest priority NAVSEA and NAVAIRcorrosion concerns are tanks/voids, insulatedpiping, valves, and hidden aircraft corrosion.These projects are managed by the Office ofNaval Research.

The Navy adopted a Condition BasedMaintenance (CBM) ACI five year Scienceand Technology program in 1996 which ismanaged by the Office of Naval Research.The goal of this program is to identify,develop and demonstrate affordable and


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robust CBM enabling capabilities to helplower costs of operating and maintaining thefleet. One of the four main thrusts of thisprogram is corrosion detection/prevention.

The Navy is in the process ofestablishing an Aging Aircraft Group andhopes to work closely with the Air Force ontheir Aging Aircraft Program.

5.2.1.2.1 Office of Naval Research

As mentioned above, ONR serves as theoverall manager for the CBM ACI S&Tprogram within the Navy. In addition tomanaging the projects highlighted belowbeing conducted by various Navyorganizations, ONR has funded FramatomeTechnologies to address the feasibility ofusing encircling eddy current to detectchanges in pipewall thickness due tocorrosion without removing insulation. Thisis being evaluated as a fast-transitiontechnology for cupro-nickel firemains.

ONR has also funded Texas ResearchInstitute to study the potential of usingguided ultrasonic waves to accomplish thissame objective. TRI is in the process ofdeveloping a pre-production prototype.ONR envisions that this technique, if provenviable, may become the main technique fordetecting corroded regions in pipes withoutremoving insulation, replacing all othertechniques including those employing eddycurrents. Unlike the eddy current technique,which is not suitable for ferromagneticmaterials such as steels, the guided wavetechnique is applicable to all metallicmaterials.

5.2.1.2.2 Naval Research Laboratory

NRL is currently investigating in-situdetection of changes in the potential ofcathodically protected tanks/voids and

correlating potential changes withdeterioration of the protective coating.Corrosion found in painted ballast tanks isassociated primarily with reduced paintthickness over weld spatter and at sharpcorners. NRL is researching different remotemonitoring technologies for corrosiondetection on the ballast of ships andsubmarines. Part of the program researchbeing carried out is to determine whether thestate of the corroding tank can be monitoredby monitoring electrochemical parameterssuch as the corrosion potential, and todevelop a correlation between the measuredpotentials and the condition of the tank. Ifsuccessful, this study would serve as thetechnology base for developing tankmonitoring procedures for the fleets.

Since the ballast tanks in the moremodern ships contain zinc anodes, a changein corrosion potential with paint degradationis expected. For the parts of the tank notcovered by water (roof and upper portionsof walls), the Navy is considering whether todevelop a monitoring technology usinggalvanic sensors embedded in the paint at thesubstrate/paint interface.

5.2.1.2.3 Carderock Division, NavalSurface Warfare Center (CDNSWC) -Philadelphia

The CDNSWC team addresses allsurface and subsurface corrosion issues andis a one-stop shop for research,development, test and implementation ofequipment, techniques and training to thefleet. Because Navy maintenance funding hasdecreased, CDNSWC strives to beinnovative and find ways to streamline theprocess. Their goals are to increase shipsystem equipment reliability, reduce costs ofrepairs and replacements, provide accuratematerial condition assessment, utilize a


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variety of technologies, transfer inspectionresponsibilities for technologies to the Fleet,and oversee Fleet maintenance.

This Nondestructive Test and Evaluation(NDT&E) group is responsible for assessinggovernment and commercial advances inNDT&E technology, investigating high costmaintenance problems, initiating NDT&Esystem joint developmental efforts,validating NDT&E systems’ performance inFleet applications, and developing Fleetinspection procedures. To this end, thisgroup has developed specific use ofinspection technologies in the areas ofacoustic emissions, eddy current, fiber-optics, infrared thermography, laser optics,ultrasonics, and magnetic flux leakage.

CDNSWC Philadelphia’s developmentalwork is primarily directed toward finding acost effective solution to operationalmaintenance problems for ships orsubmarines. However, the technology is notlimited and can be applied to multipleapplications in other government activitiesas well as the private sector. They haveaccomplished some innovative things, takingprojects from the basic research stagethrough the implementation stage. Currently,they are concentrating on shortening deliverytime to the Fleet through the use ofcommercial-off-the-shelf (COTS)equipment, where possible.

In some instances, it used to take theNavy seven to ten years from initial conceptdevelopment through to delivery of aprototype Navy system. Now, since theyare moving more towards commercialtechnology development, this lead time hasbeen drastically shortened. Some of the morecomplex Navy/commercial developments cantake three to five years. If the technologyalready exists, a performance specification

can be written to tailor the commercialsystem to Navy application within one totwo years. And if a commer-cial NDT&Etechnology to the application already existswhich the Navy can capitalize upon, thetime to procure the COTS system can befrom one to twelve months. Withequipment that this group maintains,inspections an be performed on call.

The inspection technologies that this teamuses include acoustic emission, eddy current(for condensers), electro-optics, fiber optics,remotely operated vehicles, infrared thermo-graphy, laser optics, ultrasonics, lasershearography, magnetic flux leakage, andguided wave ultrasonics. Ship systemssupported by NDT&E inspections include,but are not limited to, main boilers, auxiliaryboilers, propulsion shafting, submarine mastfairings, submarine tiles, ventilation systems,elevator wire rope, gun barrels, piping andtubing systems, main condensers, auxiliarycondensers, tanks and voids, HP air flasks,incinerator stacks, and composite structures.

Main focus areas of this team have beenthe in-place inspection of tubing, piping andhardware such as wire rope. They haveintroduced COTS equipment which haveresulted in great savings.

This activity has a number of uniqueinventions that could prove to have greatpotential for expanding into both thecommercial and other military sectors. Onespecific area for consideration is in themagnetic flux leakage technology (aderivative of eddy current technology) theydeveloped to inspect for corrosion of wirerope found on aircraft carrier elevators. Theyuse this technology to determine anyanomalies present on the surface or underthe surface of wire rope. Through use of thistechnology, the team hopes to be able to


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extend the current five year requirement forrope replacement. Applications are extensivein the mining, elevator, construction and skiindustries as well as the navies and portfacilities around the world.

Another possible dual use area is in theircontinued work on guided wave ultrasonics,which use an array of transducers. Thistechnology will be used to measure wallthickness and cracks over long runs of highpressure piping under insulation in ships andsubmarines without having to remove theinsulation. Texas Research Institute isworking with them in this area.

CDNSWC Philadelphia is examining thefeasibility of using acoustic emissions, andhas started using shear wave ultrasonics forHP air flask/LP air receiver recertifications.Acoustic emission is used extensively in thecommercial world for railroad cars andtankers. They are teaming with PhysicalAcoustics Corporation in Princeton, NJ whohave already provided them with prototypeequipment for this program. The benefit ofthese technologies is that they do not haveto cut the ship open to inspect, thus savingtime and money. It is projected thatreplacing hydrostatic/volumetric methods forrecertification with shear wave ultrasonicswill save the Navy in excess of $1M peraircraft carrier and $3M per submarine.

They are also using ultrasonic technologyfor the inspection of composite materials.Multiple equipments and structural areas ofships and submarine are being replaced withcomposite materials. Small boats in theNavy, Army and private sector are madewith composite hulls. This group is usingultrasonic inspection techniques for defectdetection and sizing, and damage assessmentand quality assurance of repairs. Also, they

have sued ultrasonics in the inspection ofHMMWVs for the U.S. Marines.

This unit has developed a number ofrobotic, remote visual inspection systemsthat


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use standard techniques to suit specificinspection needs. One of these is a RemotelyOperated Vehicle for Verification and Retrie-val (ROVVER). This device, for example,allows for the remote inspection of exhauststacks from the top, through the ship, to theengine. Another is a miniature roboticcomponent that can be used for examiningany four inch by four inch area. Other appli-cations include piping systems, propulsionshafts, gas turbine intake stacks andincinerator exhaust stacks. Co-developedwith private industry, it increases Navyinspection capabilities while decreasinginspection costs.

CDNSWC co-developed a laser optictubing inspection system in conjunction withQuest Integrated, Inc. to inspect internalsurfaces of tubing and piping for pitting andcracking. It has been used in many applica-tions, including the inspection of Army tankgun barrels. These systems are used for in-spection on main propulsion boilers and con-densers and have been distributed for Fleetuse. The savings to date realized by the Navyis $10M.

5.2.1.2.4 Naval Surface WarfareCenter, Carderock Division – Bethesda

Within the Metals Department of theNSWC, there is a Corrosion Branch (613)that conducts research into the corrosionproblems of the Navy. This branch isorganized to address three separatetechnology areas – corrosion engineering anddesign analysis, corrosion science andcoatings, and high temperature corrosion andadvanced ceramic materials. The first twoconcentrate mainly on immersion splash andspray atmospheric marine corrosion.

The Corrosion Branch is involved in thefollowing corrosion issues:

• Ship and submarine HME system corrosion problems

• System and component corrosiondesign analysis

• USMC vehicle corrosion control

• Waster sleeve corrosion for aircraftcarriers

• AC and DC electrochemical testing

• Corrosion rate measurement andprediction

• Materials selection

• Corrosion failure analysis

• Cathodic protection system designand analysis

• Seawater and marine atmosphericcorrosion testing

• Full or scale model seawater systemand component testing

• Organic coating inspection andperformance evaluation

• Corrosion modelling (computer andphysical)

• Organic and metal matrix compositecorrosion testing and analysis

• High temperature corrosion

• Corrosion control.

Some of the corrosion problems thatthey are addressing are submarine shaft sealcorrosion problems and solutions, crevicecorrosion causes and countermeasures, gal-vanic corrosion of mixed metal systems,seawater and atmospheric corrosion behavior


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of a broad spectrum of ferrous and non-ferrous alloys, and metal matrix compositecorrosion. The NSWC is exploring electro-chemical impedance spectroscopy methodsand applications to help detect the extent ofthe corrosion problems.

Their facilities include anelectrochemical test lab, a stress-corrosioncracking test lab, a high temperaturecorrosion lab, computer workstations andnetworking to a supercomputer. In addition,they have three seawater and marineatmospheric corrosion test sites – LaQueCenter for Corrosion Technology atWrightsville Beach, NC; CDNWEC in FortLauderdale, FL; and NRL in Key West, FL.

5.2.1.2.5 Naval Air Systems Command(NAVAIR)

NAVAIR is spending approximately$1B annually on expenses incurred onmaintenance and repair due to corrosion.NAVAIR researchers estimated thatNAVAIR could achieve a 25 percent savingsbattling their corrosion problems bywidespread adoption of existing techno-logies. They believe that aircraft mainte-nance could be reduced if they had an earlywarning system for hidden corrosion. Withsuch a system, NAVAIR could effectivelytransition to condition based maintenancerather than time based maintenance, fixingcomponents only when it was needed. Butfirst, NAVAIR personnel stated that theymust have in place a technology thatprovides them with a high degree ofconfidence in the data.

At the moment, NAVAIR has threelevels of maintenance: 1) on the carrier, 2)intermediate level, and 3) depot level.NAVAIR scientists asserted that if work isconducted at the first two levels, then there

is no need to have to bring the component tothe depot level. The depot level should beconsidered a last resort.

NAVAIR’s work in the area of corrosiondetection sensor technologies employsseveral different approaches which aresummarized below:

Fiber Optic - This program involvesembedding very fine fiber optic strands inone continuous length under the protectivecoatings. The strands are burned with a laserto provide a series of graduations, all ofwhich are different. The limitation here isthat the graduations must be very sharp inthe fiber. Depending on the degree ofcorrosion on the surface of the fiber, aninterference pattern is produced which canidentify the amount of corrosion and thelocation is known as the graduations generatea unique pattern. The installed position ofthe strand and its complement of graduationsis known. Research is being conducted undera SBIR program by Physical Optics inCalifornia, in conjunction with BoeingAircraft, which is very interested. Thepresent limitation of this technique is thesharpness of gratings and the amount of lightthat reflects back for discrimination.

Galva nic Sensor s - Th ese sensor s areconst ructed by electrodep osition an d vapordispo sition to form thin films. The sensorsare s elf-contai ned with a data-logg er andappro priate cat hode and a nodecompo nents. The sensor mu st be hard wired to a data logger and polled by a central compu ter either in an onb oard or of fboardsitua tion. The closer the gap betwe en theelect rode eleme nts, the g reater the sensi tivity. Th e opportun ity to var y thedegre e of corro sion measu red is ava ilableupon manufactur e as chang ing the se nsormater ials and t he gap bet ween the e lements


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will result in greater or lessor in itial andsubse quent curr ent flow g rowth with time.Senso r miniatur ization an d the radi otrans mission of corrosion current s ignals are the a reas of cu rrent rese arch activ ity, as is the c onceptual evaluation of alumin um-ionsensi tive paint compounds . Limitati ons tothese sensors a re the nee d to hardw ire eachsenso r in an ai rcraft, wh ich would add a fair amoun t of weigh t, and tha t the life span ofthese sensors i s short. F our Coast GuardH-65 helicopter s are flyi ng with th esetypes of sensor s installe d. A coulo mb plotwill allow for a measure of materia l lossbased on the fa raday equa tion. This testprogr am has bee n expanded to includ e theMarin e H-53, P- 3, H-60 an d F/A -18 testaircr aft. The A ustralians and New Z ealandAir F orce have initiated fleet test s of these senso rs. Anothe r portion of this pr ogramsuppo rts the de velopment of an ultr asonicguide d wave pro be at Penn State. Th eprobe , which us es both lo ngitudinal andtrans verse wave s, will be able to d etect wall thinn ing and de lamination due to co rrosionin ai rcraft.

Corrosion Microsensor - The thin filmcorrosion sensor technology has been takenfurther by adding an antennae, powersupply, transmitter and memory to enableautonomous remote sensing. The limitationat the moment is the thin film batterynecessary to power the unit over time. Thistechnology is still in the early researchstages.

Smart Coatings - The principle behindthis process is that ions produced bycorrosion will combine with this coatingmaterial, which will then make the coatingespecially visible under UV light. The basicproblem with this technique is in the control

to make exact homogeneous multi-ion paints.Work is continuing in this area.

Standing Wave Sensor - The NAWC has acontract in place to develop a prototype anddemonstrate the utility in 1999 for this obliqueangle ultrasonic transducer that can be used tomeasure the location and degree of corrosion.The technique requires a lot of power to bepumped into the structure, which could causeother problems. Thus, the results from thistrial are needed before any further judgmentsrelative to future utility can be made.

5.2.1.2.6 US Navy Mid-AtlanticRegional Maintenance Facility, Norfolk, VA

The U.S. Navy Mid-Atlantic RegionalMaintenance Facility, located at the NorfolkNaval Shipyard, replaced the Naval AirRework Facility (NARF) during one of theearlier base re-alignments. The facility isconsidered an intermediate maintenancefacility. As stated previously, the U.S. Navyhas three levels of maintenance: (1)organizational, (2) intermediate, and (3)depot. Organizational level maintenance isperformed as needed while systems are on-station. Intermediate level maintenance isperformed as needed when systems are inport, and is usually more extensive thanorganizational maintenance. Depot levelmaintenance is the most extensive level ofmaintenance, being typically comprised ofscheduled major overhaul and repair.

This facility is the cognizant fieldactivity for the EA-6B, and C-2/E-2 supportaircraft. They also have experiencemaintaining F-14 fighters and F-18 attackaircraft that are stationed at Ocean Naval AirStation in Virginia Beach. Since the re-alignment, their responsibilities also nowinclude maintenance on the aluminumsuperstructures of destroyers and fast


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frigates. The facility is expanding itsresponsibility even further to providemaintenance to anybody and any system inany of the services who require NDE, tryingto compete with other depots and airlogistics centers for maintenance dollars.

The NDI group at the facility iscomposed of three engineers. Manyuniformed maintenance personnel supportthe group. Their goal is to inspect and fixwhatever maintenance problems confrontthem as quickly and efficiently as possible insupport of the Navy’s readiness goals.

The basic NDE techniques they use arevisual, ultrasonics, and eddy current. Visualtechniques are used all of the time;ultrasonics and eddy current are used tofurther inspect questionable areas, ifrequired. Other techniques are used only forvery special circumstances.

The NDE staff stat ed th at th eytyp icall y do not s ee pr oblem s in lap j oints of Navy aircr aft. Parti cular prob lems theyenc ounte r are expo sed a ntenn a att achme ntpoi nts, elect rical conn ectio ns, a nd co ntrol sur faces . Rec urrin g pro blems are usual lyref erred to d esign team s to see i f the re is ared esign or r etrof it th at ca n hel p all eviat ethe prob lem.

One of the special circumstances theyhave been dealing with is corrosion in thealuminum honeycomb core of the wings andcontrol surfaces of F-18 aircraft. The basictechniques are not as useful for thesecomponents. For these problems, theengineers have found that X-ray radiographyand neutron radiography are more usefultechniques. They tend to like X-rayradiography better because it’s cheaper thanneutron radiography and because they haveto ship components to McClellan AFB in

Sacramento in order to utilize neutronradiography.

5.2.1.2.7 Jacksonville Naval AviationDepot

The Jacksonville NADEP providesdepot level maintenance for P-3, S-3, EA-6B, and E-6 support aircraft, F-14 fighters,and F-18 attack aircraft. The NADEP alsoservices TF34 and J52 jet engines. Theemphasis during depot maintenance of thesesystems is on corrosion detection andprevention. Corrosion inspections areconducted to better understand trouble spotson each aircraft or engine. A typicalcorrosion inspection for a P-3 takes 30 days.

The predominant technique used toinspect for corrosion at the NADEP is visual.NDE techniques are used to supplement thevisual inspections and for particularly toughinspection areas. NDE technologies beingused by the engineers at the NADEP areliquid penetrant, eddy current, ultrasonics,magnetic particle, x-ray radiography, andcomputed tomography. Thermography israrely used. The engineers are not bigproponents of neutron radiography. Theyunderstand that it is very sensitive tohydrogen, and thus water, which may causecorrosion, but the cost of implementation isprohibitive.

In the area of corrosion prevention, theNDI team discussed a number of techniquesthat they think hold great promise. Exteriorcorrosion problems could be alleviated bywashing down the aircraft after each mission.This would remove any salt or othercorrosive from the surface of the aircraft.Dehumidification or forced air storageshelters for aircraft should be used to keepthem free of moisture. They also believedthis could be further enhanced by requiring


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future aircraft to be designed with air “flow-thrus” in the body of the aircraft to reducethe amount of trapped moisture. Lastly,they discussed the increased use of corrosivepreventative coatings. The engineers at theNADEP stated they are currently testing aproduct called “Dinol” that is usedextensively by the Australians on all of theiraircraft with very good results.

5.2.1.2.8 North Island, NAVAIR

North Island does major, depot-levelaircraft overhauls lasting from 6 months to 1year in duration. It is similar to the NADEPat Jacksonville, in that it works on F/A-18,E-2, C-2, F-14 and S-3 aircraft. Their focusin the area of corrosion is on maintenance-type prevention using new sealants. Theyuse standard visual, ultrasonic, eddy currentand x-ray techniques for corrosion detection.The NDE specialists stated that the E-2 andC-2 airframes are the Navy’s biggestproblems, due to their age. The S-3s haveproblems with corrosion, but this isprimarily caused by the aircraft’s design andis being corrected as the airframes undergore-work. All F/A-18s receive an annualvisual inspection by field teams sent outfrom North Island. The Navy uses 52-dayinspections (primarily visual) at theorganizational level to look for corrosion inthe field and that the intermediate level ofmaintenance uses eddy current andultrasonic techniques.

5.2.1.2.9 Pearl Harbor Naval Shipyard(PHNSY), Pearl Harbor, HI

The PHNSY personnel indicated thatone of their primary corrosion problems waswith bronze bearing shells, located under themain propulsion shaft on ships, that oftencorrode badly due to their frequentimmersion in seawater. The machining

needed to cut out any corrosion is expensiveto perform. The use of galvanic straps hasmitigated, but not eliminated, the problem.While any corrosion is detected visually(using boroscopes), this still requiresremoval of rubber bearing elements. Thenonce these are replaced, it often is found thatthe receiving area also has corroded, aproblem which often is not/can not berecognized until the first repair is made,adding a further cost. The bearing shellcorrosion problems have been seen only inwarm water climates.

Another significant problem the PHNSYteam has encountered is corrosion androtting of rubber on board naval vessels,especially on submarines. Large pieces ofequipment are often mounted on resilientrubber mounts in order to reduce emittednoise. If visual inspection determines thatthe mounts have swollen, they are replaced.However, it is not known if the mounts canfail without swelling and there is no way totest to see if non-swollen mounts havefailed. For instance, it is not possible todetermine aboard ship whether a mount iscompressed because it is under load orbecause it has failed.

The representatives also mentioned thatcorrosion and the condition of air intakes iscritical. These intakes gather fresh air andfeed it to the ship’s power turbines. Due tothe salt-laden nature of the maritime airwhich is ingested, the intakes are subject tocorrosion. The attendees did not know whatother technologies might be appropriate, butestimated that 99 percent of the inspectionsperformed at present in the fleet on theseintake valves are performed visually. Theyalso commented that aluminum forms a self-sealing oxidation layer. Thus, it may be


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impossible to avoid the formation of someoxidation on its surface.

The representatives commented that inthe Navy’s environment as a whole, butespecially in the submarine world, there is anoperational aspect to the cost of corrosion: itcan contribute to an increase in emittednoise, reducing the operational effectivenessand survivability potential of the vessel.

On the structural side, most NDI isperformed visually, especially in otherwiseinaccessible areas. Often, these inspectionsoccur at sea. In fact, accessibility limits theareas where even visual searches can beperformed, since often access to even one sideof a structure or piece of equipment isdifficult. In addition, often the surfacepreparation required to perform an efficientNDT effort is so extensive that it is notfeasible to perform the test/inspection. Aspecific example cited was that of condensertubes, for which reliable methods of inspection(eddy current) exist, but for which thepreparation is very time-consuming.Consequently, in many cases, often only ageneral idea of the material thickness remainingin an area undergoing inspection is available inan area of general pitting. Eddy current is usedto test/inspect tubing aboard ships,radiography is used to check pipes (it wasstated that safety considerations are not asgreat a concern here), and visual inspectionsare used on hulls.

One representative stated that there is nosuch thing as a non-visual non-destructivetest of the glass-reinforced plastic used insonar systems since the material “breaksapart.”

One major impediment to maximizing thebenefits gained from the inspections whichare performed is that often Shipyard

personnel do not have the basicinformation/specification on the piece ofequipment or material which is being tested.They often are told by the OEMs that thedetails of the equipment which is undergoingtests are proprietary, even though theGovernment usually purchases and shouldreceive engineering drawings for use in themaintenance and repair of the equipment atthe time of its procurement. This problem isespecially prevalent in the surface craftcommunity.

Again in the area of structures, andespecially submarines, it was said that mostof the materials being dealt with in the Navycommunity are thick, and the view of theparticipants was that proper installation andpreservation will prevent corrosion. Thus,they do not view external corrosion as asafety/structural problem (as the aircommunity does) and see no need for specialNDI equipment to detect/combat it. If anarea of a hull (even a submarine hull) iscorroded extensively, it can merely be cutout and replaced. Cutting through hulls is, infact, a standard procedure, since itfrequently is done to gain access toequipment in interior compartments whichcan be reached in no other way. It often isnot even necessary to put the ship indrydock to perform such repairs, althoughsubmarines generally are repaired indrydock.

The Shipyard is able to buy its own NDIequipment out of its own budget, so if a newpiece of equipment/technology can bejustified, it can be purchased. Therepresentatives were asked about theirability to introduce new NDI technologiesinto use at the Shipyard. They are notsubjected to the same constraints as theaircraft industry, where the FAA and OEMs


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often restrict the use of new technologies toperform corrosion detection for safety orpotential liability reasons. Instead, since theShipyard operates on limited funds, thecost-effectiveness of any new system mustbe demonstrated if it is to be procured andused. Any new system must be inexpensiveenough to be affordable in terms of bothprocurement and operator training costs.

5.2.1.3 U.S. ArmyIn the corrosion arena, the Army has

placed most of its emphasis on corrosionprevention technologies rather thancorrosion detection technologies. The Tank-Automotive and Armaments Command(TACOM) was directed by the ArmyMateriel Command to develop a CorrosionPrevention and Control Program to addressthe concerns for Army weapon systemcorrosion.

Part of the impetus behind this programwas the serious corrosion problems affectingthe U. S. Army Pacific fleet. The fleet wasunable to maintain the vehicles withoutfrequent replacement of exterior items.Vehicles were succumbing to rust andneeding to be replaced within 15 years ofservice life. The Army estimates that thePacific Fleet has to spend approximately$4M per year on vehicle corrosion controland prevention in order to keep the fleetmission ready. The Pacific Fleet hasembarked on a rustproofing/paintingprogram to extend the life of the current fleetby five years.

The Picatinny Arsenal is spearheadingthe CPC effort for TACOM. The objectivesof this program are to decrease life-cyclecosts, increase Army readiness by reducingequipment down time, and reduce themaintenance burden being placed ondiminishing active and reserve work force

resources. The CPC program has empoweredCorrosion Integrated Product Teams at allAMC Subcommands whose efforts arecoordinated by an AMC CorrosionAbatement Team, chaired by the AMCCorrosion Manager. A major focus of theprogram is on policy issues to ensure that themost appropriate and economical corrosioncontrol technologies are included in allweapon system designs, and that CPC is partof the materiel release process for newacquisition and rebuild programs. Its goal isto ensure that AR and DoD policy places theresponsibility for user’s cost of ownershipwith each Weapon SystemManager/PM/PEO throughout theoperational phase.

To address the science and technologyissues, a two-pronged attack is beingimplemented: 1) identify, test andimplement the latest CPC state-of-the-artpractices available in industry, and 2)develop, verify and implement newtechnologies to reduce corrosion in new andfielded systems.

Finding noninvasive ways to detecthidden corrosion is part of the Army CPCplan. The Army is studying newtechnologies that are less manpowerintensive than those used in the past, with afocus on automating the decision makingprocess. Sensor technology is one of themajor Science and Technology R&D areas ofthe program, particularly for use in locationsrequiring major disassembly or destructivedisassembly for inspection.

5.2.1.3.1 U.S. Army ResearchLaboratory (ARL), Metals Research Branch

The Metals Research Branch of the ArmyResearch Laboratory is the primary researcharm in the Army concentrating on the Army’s


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corrosion problem. Their main focus is oncorrosion prevention through coatings.

However, ARL has studied a number ofthe different technologies that we areaddressing in this study for corrosiondetection. The lab, though, has examinedthese technologies more for use at themanufacturing level and/or to inspectproduction line tools for qualitymeasurement. The techniques are the samebut the setup and utility are different.

NDT developments that ARL ispursuing include detecting stress fatiguecracking/stress corrosion using acousticemission technologies. This entails pickingup acoustic emissions from samples while itis stress corroding.

ARL is also developing electrochemicalimpedance spectroscopy techniques tomeasure the first beginnings of coatingdeterioration. This technology is not easilyadapted to aircraft because the inspectorswould not be able to ascertain what ishappening at the rivets.

X-ray images are being investigated usingcomputer topography to develop 3-Dimages that neural networks can analyze forfault detection. One application this is beingused for is for inspecting artillery fuses.

Ultrasonic C-scan transducerdevelopments are being researched thatwould allow explosive armor to becharacterized initially and then tracked overtime on a vehicle to determine its protectioncapability. ARL has two emergent tanks forscan analysis.

In the acoustics arena, ARL is workingwith a Chicago company, SANTECCorporation, which is developing a ”2X2”sensor that will provide a one shot C-scan

equivalent representation of both flatsurfaces and around shapes. This showsgreat promise for armored vehicles.

In the visual domain, the focus of thework is to develop neural networks for anauto analysis of digitized video. To do this,however, destructive tests are required totrain the networks. The advantage to thistechnology is that you will not have to trainpeople for repetitive inspections. Thepotential application to corrosion detectionis evident but off in the future.

ARL also has eddy current andthermography capabilities. They have notdone any research in the eddy current areafor a few years. ARL uses the thermographylaboratory at the University of Delaware.

5.2.1.3.2 Army Research Laboratory(ARL), Vehicle Technology Center

ARL has an office with five NDEtechnology researchers in the same buildingas the NASA NDE researchers as a result ofgovernment consolidation. They are workingon a number of joint NDE research effortswith NASA Langley researchers (see NASALangley writeup).

5.2.1.3.3 Army Aviation MissileCommand, Depot Maintenance EngineeringTeam

The Depot Maintenance EngineeringTeam is responsible for all engineering insupport of Army aviation maintenance.They are the lead organization responsiblefor reviewing corrosion prevention andcontrol for aircraft. There are approximately30 engineers on this team. One of their majorprograms is conducting an AirframeCondition Evaluation (ACE) annually. Thisinvolves sending teams of inspectors to goout and examine aircraft for indicators of


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wear and tear, among other things. Theobjective of this program is to prioritizeaircraft for overhaul, in a move towardsoverhauling aircraft based on condition basedmaintenance rather than at set intervals. Theteam recently created additional points toadd to their checklist to look for corrosionindicators. They work in coordination withthe other Services, sharing data on H-60helicopters.

5.2.1.3.4 U.S. Army Pacific, Ft. Shafter,HI

The Science Advisor for USARPACnoted that the most pervasive and expensiveproblem in the Pacific is corrosion. The25ID(L) spent $11.6M, FY79 - FY84, torepair corrosion on 1,919 vehicles. Thecurrent program (FY96 - FY98) will spend$5.9M to repair corrosion on 3,700 vehicles.And USARHAW still has 1800+ pieces ofequipment in need of corrosion repair.

She noted that the solution is multi-faceted:• ground vehicles and aircraft must be

designed with corrosion resistantmaterials and runoff should beencouraged or areas sealed to prevententry of seawater;

• equipment shipped overseas should besprayed with a rust inhibitor prior

to shipment;• expensive equipment should be stored in

dehumidified shelters or expensiveelectronic sections of vehicles/aircraftshould be dehumidified separately;

• corrosion prevention must be given highpriority in maintenance programs byproviding necessary tools, training, andtime.

All of these - design, materials,preventive measures, storage, and propermaintenance - must be undertaken toalleviate this pervasive problem.

The SA has been continuing discussionswith TACOM PMs, requesting thecorrosion issue be a strong influence onfuture upgrades and requesting theapplication of a rust inhibitor to newequipment prior to shipment. SA has drafteda letter from LTG Steele, CG, USARPAC,to MG Beauchamp, CG, TACOM,requesting Carwell Rust Inhibitor be appliedto all ground vehicles sent to USARPAC.Carwell has been proven to be effective inabsorbing moisture and providing aprotective coating against corrosion withoutadversely affecting the CARC paint. It isone of the five anti-corrosion productswhich successfully passed the Fielded FleetCorrosion Control Program conducted byMaterials Modification Inc. and reported inJuly 1997. The five products reduced meantime to repair (MTR) by at least 30 percent.

A two-and-a- half week CorrosionPrevention and Control (CPC)demonstration and course will be held 27April - 8 May for welders and motor poolpersonnel at the 25ID(L). 9thRSC,HiARNG, and USARJ personnel will beincluded. A vacublaster and Sulzer MetcoFlame Spray equipment will be delivered toDOL Shop 5, 25ID(L). TARDEC willprovide a welding review and certification.The vendors of the various products willteach grit blasting; and the application ofSulzer Metco flame spray, Zingametall,Ziebart, and Carwell. Mr. HowardMiyamoto, Industrial Hygiene, will addressissues associated with the touchupapplication of CARC paint. TARDEC is


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funding the welding review; AMC FASTfunded the equipment and some of thetraining.

The Science Advisor provided anoverview of the status of various systems:• GROUND VEHICLES: Upgradesincluding better corrosion-resistant materials(galvanized GP90, stainless steel, aluminum)and designs to discourageentrapment/encourage runoff are coming orare planned for various ground vehicles fromTACOM.• FMTV: COL Dobeck, PM-FMTV,will have the Carwell Rust Inhibitor appliedto all 1196 FMTVs to be shipped toUSARPAC in FY98 and FY99; thesevehicles will have the advantage of upgrades($2500 per vehicle) geared to corrosionprevention, the funding for which wasobtained by COL Dobeck, Oct 96.• HEMTT: USARPAC will benefit fromthe many changes to the HEMTT over thelast 10-15 years - welding changes, drainagetubes instead of trapping of water in earlierdesigns - in the FY98 delivery of 14HEMTTs. PM-HTV is considering anEngineering Change Proposal (ECP) toprovide galvanized cabs, dielectric coatingsfor electronics and stainless steeltubing.which could enhance future HEMTTprocurements.• PALLETIZED LOADING SYSTEM(PLS): PM-HTV will coat the PLS-1075scoming to USARPAC with zinc chromateprimer at a cost of $6K apiece.• M129 TRAILERS: PM-TAWS isplanning to replace the 17 M129 trailers atUSARPAC with aluminum trailers.• 1022A1 DOLLY SETS: ESCO hasprovided pre-galvanized or hot dipgalvanized steel components as well as

corrosion resistant hardware in the dolly setsjust received by USARPAC.

• ROTORBLADE AIRCRAFT:USARPAC has recently received 32Blackhawks (UH60L) made by Sikorsky.The 25ID(L) has an effective CorrosionPrevention and Control program; acontractor, LMI, is the second line ofdefense in corrosion after the unit. The unittakes advantage of a corrosion preventionclass provided by the Navy at Barber'sPoint. None of the aircraft is 'stored'.Sikorsky has an active Corrosion Preventionand Control (CPAC) group, Team Hawk (aquad service) and sponsors Users'Conferences geared for maintenance officersand chaired by the PM. Recommendationsare provided as to treatments, assembly, andtesting of corrosion-prone areas and a tri-service corrosion manual for fieldcommanders has been developed.AMCOM recommends a zinc chromatespray for corrosion problems.

Maj C hiles, Dep uty Suppor tOpera tions Offi cer, 45CSG , has deve lopeda Cor rosion Pre vention an d Control Planwhich has been approved b y BG Campb ell,Deput y Commande r Support, 25ID(L). SAplans to work w ith COL Th ompson,Comma nder, 45CS G, and Maj Chiles in build ing justif ication fo r funding of sorelyneede d vehicle wash facil ities at S chofieldBarra cks and th e Pohakulo a Training Areaon th e Big Isla nd where 2 5ID(L) con ductsmuch of its tra ining. SA also plan s toconsi der a mix of equipme nt at 25ID (L) indeter mining the equipment for which dehum idified st orage woul d be justi fied.The S cience Adv isor noted that effe ctive,long- term maint enance is the last, but mostimpor tant piece of the Co rrosionPreve ntion and Control Pr ogram. She


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asser ted that, without it , vehicle redesignsand u se of bett er corrosi on-resista ntmater ials will have been for naught .

5.2.2 Marine CorpsAs with the other Services, corrosion is a

major concern of the Marine Corps. Duringthe Desert Storm build-up, Camp Pendletonidentified major environmental complianceissues surrounding Chemical Agent ResistantCoating (CARC) application. Assetsreturned from SWA highlighted the corrosionproblems in the Marine Corps.

The Marine Corps procures mosttactical ground equipment through otherServices. For example, wheeled vehicles,tanks and engineering equipment (i.e., airconditioners, generators, water purificationequipment, etc.) are procured by the Army.Additionally, Marine Corps equipment istransported by ship, and operated in coastalareas, jungles and deserts. This contributesto a severe corrosion environment. As aresult, incorporating Marine Corps corrosionrequirements requires extensive coordination,in addition to identifying corrosionrequirements.

Within the corrosion arena, the MarineCorps’ major emphasis is on corrosionprevention and control and they have aprogram in place to address these issues.The Marine Corps Corrosion Prevention andControl (CPAC) program was formallyestablished by MCO 4790.18 dated 20 June1994. The order provides policy for themanagement and execution of the MarineCorps CPAC program, placing managementresponsibilities at Marine Corps SystemsCommand (MARCORSYSCOM), Quantico,Virginia, with policy and oversightresponsibilities residing at Headquarters,United States Marine Corps. The twoprimary elements of the program are

preventive corrosion control and correctivecorrosion control. Preventive measuresinclude acquisition support and technologyinsertion. Acquisition efforts focus onincorporation of adequate corrosion controlmeasures during the design and productionphase. Technology insertion involves theevaluation of commercial products forapplicability to Marine Corps tacticalground and ground support equipment. Partof this effort entails evaluating maintenanceprocedures and recommending changes.

As the Marine Corps prepares to enterthe next century, many factors will impactthe Marine Corps’ ability to maintain acombat ready posture. One area that canbenefit from technology and a joint servicepartnership is corrosion. The Marine Corpshas developed a Plan of Action andMilestones as their strategy for the future.This strategy focuses on product andprocess improvement, training andeducation, partnerships with other Servicesand private industry, and other futuristicinitiatives. Their underlying intent is toreduce or eliminate duplication of corrosionprevention efforts within the Department ofDefense and have laid the groundworkthrough much interaction with acquisitionagencies and groups such as NACE and theTri-Service Conference on Corrosion. Theirvision is for an integrated corrosion controlworking group at the highest level to addressthe problems of today and prevent theconsequences of tomorrow.

The first effort pursued by the MarineCorps CPAC program was fielding areplacement for CARC. CARC gives MarineCorps equipment its camouflage pattern butenvironmental restrictions in SouthernCalifornia limit the amount that can beapplied. Headquarters Marine Corps


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directed that an alternative be found.Extensive testing resulted in a coating thatmet all camouflage requirements but was notresistant to absorption of chemical agents.This coating, now in use throughout theMarine Corps, is referred to as WaterborneCamouflage Coating (WBCC). It is theprecursor of the Waterborne CARC beingdeveloped by the Tri-Service SERDP effort.

A major effort to incorporate corrosionrequirements into acquisition documents hasbeen initiated. Acquisition reform hasmandated a fresh approach to procurementpractices within DoD. No longer can MIL-Specs and Standards be used at will.Corrosion requirements must be translatedinto performance language. Basically, theServices must tell a prime contractor what isrequired, not how to meet the requirement.As a result, corrosion requirements must beidentified in terms of operationalenvironment and required useful life. Teststo verify conformance may still be invoked.Generic wording for all acquisitiondocuments required by DoD 5000 is beingdeveloped by a team composed of corrosionand acquisition personnel. Tailoring will bedone for specific programs.

The Marine Corps is comparingaccelerated test data from GM 9540P/B andASTM G85 and B117 to marineatmospheric performance of metals andcoatings. The objective is to identify the bestmethod to verify conformance of a productto performance specifications.

The Marine Corps is currentlyevaluating corrosion improvements for manyMarine Corps vehicles. Materialsubstitutions for exhaust systems, fuel andbrake lines and head lamp assemblies forHMMWVs and 5-ton trucks are beingevaluated in marine atmosphere and field

tests. Thermal spray aluminum is beingevaluated for specific failure points on bothvehicles, such as hard top latch, rear cornerpanels, door frames and posts and roofgutters on HMMWV and cab floor, hoodcowl and tool boxes on 5-ton truck. Thermalspray plastic was applied to 5-ton batteryboxes. Tests evaluating additives towashdown water and crevice coatings werealso initiated.

Corro sion engin eering sup port toProgr am Manager s withinMARCO RSYSCOM is a major e mphasisof th e Marine C orps progr am. While lifecycle cost data to suppor t corrosio nupgra des is dif ficult to obtain, th e corrosio nrelat ed mainten ance burde n is signi ficantenoug h to justi fy the imp rovements. Thiseffor t includes design an alysis, ma terial and coati ng selecti on, evalua tion of fl eetcondi tion, sour ce selecti on criteri a, andenvir onmental a nd mainten ance impac ts.This work is do ne in coor dination w ithother Services.

Environmental compliance issues plaguemost Marine Corps locations. Efforts tofacilitate organizational maintenanceprompted evaluations of surface preparationequipment and surface tolerant coatings.Other efforts to evaluate underbody coatingsare underway. These efforts support fieldedequipment and can be incorporated into newacquisition initiatives.

Controlled humidity preservation ofequipment is being pursued for fieldedequipment to isolate the equipment from itsenvironment.

A USMC Corrosion Control Web Site isbeing developed to encourage informationexchange within DoD. This web site willprovide information on the Marine Corps


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corrosion program and provide access to testdata.

5.2.3 Canadian DND ActivitiesThe Canadian Department of National

Defence (DND) has several differentdepartments and laboratories researchingcorrosion detection and corrosion preventiontechnologies. These groups are extremelyeffective in coordinating their researchactivities. Most R&D efforts are handled atAVRD and NDHQ. Applications are thendeveloped and tested at ATESS. Thoseapplications which are proven effective arethen put into use in the field at area facilitiesand wing engineering maintenance centers.

A predominant focus of their research ison corrosion prevention and detection inaircraft. The Air Vehicle ResearchDetachment/Structural and Materials Groupoversees R&D in these areas.

5.2.3.1 Air Vehicle ResearchDetachment

The Air Vehicle Research Detachment(AVRD) is a CRAD organization formedwith the goal of providing a focus for, anddelivering, air vehicle research anddevelopment. One of their R&D thrust areasis the Air Vehicles Thrust, which is aimed atreducing the costs of DND aircraft operationswhile maintaining or improving airworthinessstandards. A large portion of the structuresand materials activities are conducted undercontract by the National ResearchCouncil/Institute for Aerospace Research asone large project under this thrust. Manyprojects are also initiated in collaborationwith the NRC/IAR. The AVRD houses an

NDT laboratory with state-of-the-art eddycurrent, ultrasonic and real-time radiographicequipment in addition to an enhanced visualD-Sight system. Most in-house activitiesfocus on the detection of hidden corrosionand cracks under fasteners.

The AVRD and the NRC/IAR/SML areinvestigating technologies and advancedmaterials for improved corrosion resistancein aging aircraft. Both organizations are alsoresearching a wide range of techniques tonon-destructively inspect high prioritycomponents and address recurrent structuresand materials problems.

AVRD cited six examples to highlight theincreasing age of the air fleet which arepresented in Table 5-1. AVRD believes thatthe primary corrosion problems in the fleetstem from the use of 7075-T6 aluminumaircraft structures, particularly the Herculesand Aurora fleets. The harsh environmentsin which these aircraft operate also is a largecontributor to the corrosion problems.

AVRD and NRC/IAR/SML areresearching the entire spectrum of NDTtechniques for corrosion detection.Researchers at NRC/IAR, with early fundingsupport from AVRD, developed the “D-Sight” technique with Diffracto. They arecontinuing to work to optimize thetechnique. They claim that D-Sight can nowdetect 3 percent material loss. They havetwo current ongoing contracts related to D-Sight with U.S. Air Force OEMs, one ofwhich is with Northrop Grumman in LongBeach, CA. They are also researchingadvanced optical, eddy current, guided waveultrasonics, and real-time x-ray techniques.


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AVRD is collaborating with QETE, theRoyal Military College (RMC) and theAerospace and TelecommunicationsEngineering Support Squadron (ATESS) tosolve its CF-18 rudder and aileron wateringress problem. The goal of thiscollaborative effort is to quantify how muchcorrosion is too much or, stated anotherway, what is the corrosion threshold atwhich the CF-18 fleet can still operateeffectively.

The program directors at AVRD haveunderway a project performed at RoyalMilitary College on a knowledge basedsystem, which will make corrosionmaintenance information more complete andeasily retrievable as well as allow theintegration of data from various sources,including that from NDT and future on-linemonitoring sensors. This information systemwill aid structural integrity managers makingairworthiness decisions and rationalizingmaintenance inspections related to corrosiondamage.

They have also undertaken a corrosionsurveillance project to reduce maintenancecosts by optimizing corrosion preventionactions and inspection schedules. Thisincludes data from environmental sensors

and on-board optical sensors to monitorcorrosion activity.

Other advanced NDT technologies beinginvestigated in-house by AVRS personnelare pulsed eddy current, dual frequencyeddy current scanning, and enhanced imagingmethods in ultrasonics. Collaborativeprojects are also in place with NRC/IAR andIMI to investigate air coupled ultrasonicsand laser ultrasonics for hidden corrosiondetection.

5.2.3.2 Institute for AeropsaceResearch (IAR), National ResearchCouncil Canada

The NRCC/IAR has an NDI laboratorywith state-of-the-art eddy current, ultrasonicand real-time radiographic equipment inaddition to an enhanced visual D Sight andEdge of Light (EOL) systems. In-houseactivities focus on the detection of hiddencorrosion, cracks, defects in compositestructures and disbonds in bonded joints.The NRCC/IAR is investigating technologiesand advanced materials and processes forimproved corrosion resistance in agingaircraft. NRCC/IAR is also researching awide range of techniques to non-destructively inspect high prioritycomponents and address recurrent structuresand materials problems, inspection reliability

Table 5-1. The Aging Canadian Forces Air Fleet.

Aircraft Aircraft Age Projected RetirementDate

CT “T” Birds 45 years old 2005

CT114 Tutors 34 years old 2015

CC130 Hercules 33 years old 2010

CP140 Auroras 18 years old 2010

CF18 Hornets 15 years old 2010

CH 124 Sea Kings 35 years old 2005


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assessment as well as NDI signal processing,pattern recognition and neural networks.

Researchers at the NRCC/IAR helpedDiffracto Limited develop the D Sighttechnique for aircraft NDI with funding fromDND/AVRD, Transport Canada, FAA andUSAF. Work is continuing to work tooptimize the technique and to developquantification capabilities. that theNRCC/IAR has demonstrated that D Sightcan reliably detect 3 percent material loss inlap joints. Collaboration continues betweenDND/AVRD (located in the NRCC/IARbuilding) regarding research of the entirespectrum of NDT techniques for corrosiondetection. The NRCC/IAR is alsoresearching advanced optical Edge of Light(EOL), eddy current, guided waveultrasonics, air-coupled ultrasonics, and real-time x-ray techniques. Collaborativeprojects are also in place with IndustrialMaterials Institute (IMI) of NRCC toinvestigate laser ultrasonics for hiddencorrosion detection in lap joints andexfoliation under faster heads in thick sectionstructures. Naturally and artificiallyexfoliated specimens (using an NRCC/IARdeveloped process) are included in thisproject. This project is partly sponsored byDND /AVRD.

The NRCC/IAR has developed one ofthe largest Aging Aircraft SpecimenLibraries. Over 300 fuselage and wingsections have been collected fromdecommissioned aircraft (Boeing 707,727,737 and 747, Douglas DC-9 and DC-10,Lockheed L1011, Bombardier CL-600).These specimens have been inspected withvarious NDI systems and the data is enteredinto a database along with AutoCADdrawings. Many specimens contain naturalcorrosion and cracks. Some have been

artificially corroded using an SMPLdeveloped process. The specimens are usedby the NRCC/IAR and other organizationsto develop NDI systems. For example,including SANDIA Labs who havecontracted NRCC/IAR to supply specimensfor their corrosion NDI validation work(FAA AANC) and several EuropeanLaboratories have also contracted theNRCC/IAR for similar services.

The NRCC/IAR is being supported byAVRD to develop a capability to performdata fusion on a wide variety of NDTtechniques. Currently, D Sight and EOLinspections of lap splice joints have beeninterpreted by data fusion processes on acomputer, and research is being carried out infusion of D Sight/EOL with pulsed eddycurrent inspections of airframe components.

The NRCC/IAR has current ongoingcontracts related to corrosion-fatigue withDND, USAF and OEMs. One of the keyaspects of these projects is the developmentof corrosion metrics using various NDIsystems.

5.2.3.3 Quality Engineering TestEstablishment (QETE)

The role of the Quality Engineering TestEstablishment (QETE) is to work with thevarious research organizations in Canada todevelop efficient and effective techniques forCanadian Forces maintenance detachments inthe field.

The primary effort ongoing in thecorrosion detection/NDT area at QETEconcerns an ongoing examination of wateringress into the composite Al honeycombstructure of CF-18 rudders and ailerons.Upon examining the issue closely, QETEengineers found that 65 percent of CF-18rudders and ailerons were experiencing some


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quantity of water ingress that was leading tocorrosion in the aluminum honeycombstructures. When QETE consulted with theU.S. Navy about the problem, theydiscovered that the U.S. Navy simply scrapsany rudder or aileron that is found withwater ingress. The Canadian Forces,however, does not have the resources toreplace every rudder and aileron thatexperiences water ingress.

In order to address the problem, QETEengineers have initiated an effort to try andquantify how much water ingress, andtherefore how much corrosion, is too much.They are testing sample CF-18 damagedrudders and ailerons using through-transmission ultrasonics and X-rayradiography. The QETE engineers considerthat neutron radiography and thermographyprovide them with a good representation ofthe amount of water in the structures.

5.2.3.4 Aerospace andTelecommunications EngineeringSupport Squadron (ATESS)

The mission of the Aerospace andTelecommunications Engineering SupportSquadron (ATESS) at CFB Trenton is toprovide critical aerospace andtelecommunications engineering, specializedtraining and production in response toongoing maintenance, installations and urgentoperational requirements. ATESS has anannual operating budget of $15M.

NDT is one of ATESS’ manycapabilities, in that they are responsible forthe actual development of NDT techniquesthat are implemented in the field. ATESSinspection technicians utilize both basic andadvanced NDT methods. The basic NDTmethods used by ATESS inspectiontechnicians are:

• Liquid penetrant inspection (LPI)

• Magnetic particle inspection (MPI)

• Ultrasonic inspection

• Eddy current inspection

• X-ray and gamma ray radiography.

The advanced NDT methods used byATESS inspection technicians are:

• Robotics scanning system

• Diffracto D-Sight

• X-Ray film digitizer

• Shearography

• Thermography

• Optical prism system

• Multi-directional MPI system.

In regards to thermography, rather thanhaving a pulsed thermography system suchas the system being developed by WayneState University and Thermal Wave Imaging,ATESS instead uses a portable hand-heldheater as the heat source. They use a similarinfrared camera.

5.2.4 Australian DoD ActivitiesThe major Australian DoD research arm

involved in studying corrosion detectiontechnologies is the Defence Science andTechnology Office. The Office has a numberof divisions addressing different corrosionissues and technologies to employ to detectand correct corrosion. There is a high level ofcoordination between these divisions. Apredominant focus of their work is on agingaircraft as well. A summary of the currentR&D activities is provided in the followingsections.


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5.2.4.1 Defence Science andTechnology Office (DSTO)

The role of t he Ai rcraf t Cor rosio nCon trol, Mari time Platf orms Divis ion, isto help the A ustra lian Defen ce Fo rces(AD F) co ntrol and preve nt co rrosi on in Fix ed an d rot ary w ing a ircra ft an d shi ps.The Airc raft Corro sion Contr ol, M ariti mePla tform s Div ision cons ists of 12 - 15 res earch ers. Their work is s ponso red b ythe RAAF (whi ch co vers Army needs ) and the RAN.

Australia flies a number of older aircraftand has found that corrosion is a majordriver of aircraft lifetime, overtaking fatiguecracking. One DSTO representativeestimated that the cost of corrosion inAustralia runs to $25M - $30M AUD peryear (scaling off the 1990 USAF study).

AMRL controls the total value of theirstudy program, but decides on the projectsstudied in consultation with the RAAF andRAN. Ten percent of their budget is devotedto enabling R&D projects. One ongoingproject is to implement corrosion databasesto quantify whether their work is impactingcorrosion. However, they admitted that inthe past funding was hard to generate for thetypes of projects performed by this group,but this is changing.

The division conducts research over abroad front. The first is environmentalcharacterization. That is, AMRL’s job is tocharacterize and monitor the operationalenvironment of the aircraft, including theenvironment/climate at the RAAF bases,since the aircraft spend 90 percent of thetime on the ground. This characterizationincludes the development of sensors andmonitors for use inside the aircraft, tomonitor both the environment and corrosiongrowth. An example is in the tail of the P-3

near the rudder torque tube. Sensors placedhere ensure that when the environmentbecomes “aggressive,” the contaminantspresent will be known. This type ofmonitoring is to be expanded to other siteswithin the P-3. The sensor used is based ona galvanic pile, and includes a self-contained,battery-powered (with a 2-month lifetime)chip. Other sensors will be placed in F-111s,but will use a linear polar design to measurecorrosion rates in situ, allowing AMRL tochoose better coatings.

A second area of interest is corrosionprevention. This includes the testing (butnot the research and development into)paints, sealants, new alloys, and CPC-freesolvents.

Another area of interest is corrosioncontrol. Here, AMRL tries to detect, sizeand watch the growth of corrosion, removingit only when necessary. This covers threespecific sub-areas. The first is the study ofcorrosion prevention compounds. Here,compound life is key, so that determinationof the best means to apply them is essential.A second corrosion control sub-area isaircraft washing in which the careful choiceof detergents which clean, inhibit corrosion,and leave little residue is being examined.The third sub-area is dehumidification. Thisis attempted wherever and wheneverpossible. The DSTO representativesmentioned that while 501 Wing at Amberley(see 5.2.4.4) is unaware of this effort, theflight line personnel in operational squadronsknow of it and attempt to placedehumidifiers near each parking point on theflight line. In addition, the F-111Gs recentlyreceived from the USAF which are to bekept in storage will be kept in dehumidifiedspaces. Such dehumidification facilities costonly $5K - $10K AUD per unit.


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AMRL also studies the interaction ofcorrosion and fatigue. Their belief is that ifthey are going to leave corrosion in place tomonitor its growth and impact, they mustknow how it interacts with stress loading,especially on plane surfaces and at fastenerholes.

The Aeronautical and Maritime ResearchLaboratory is also involved in eddy currentresearch. The NDE Research group isprimarily focussed on the research on themainstream ultrasonic and eddy currenttechniques to quantify corrosion andcracking in RAAF aircraft and Navy shipsand submarines. The group also hasspecialist expertise in a range of acoustic andelectromagnetic techniques. The NDEresearch group has a wide-ranginginternational collaboration program ondefence related NDT, especially with theUSA, Canada and UK under The TechnicalCo-operation Program. A second AMRLgroup focuses on applied development andperforms inspections. A representativefrom this group stated that AMRLintroduced NDI into the RAAF about 20-30years ago. Nationally the CommonwealthScience and Industrial Research Organization(CSIRO, an analog to Canada’s NationalResearch Council) and the AustralianNuclear Science and TechnologyOrganization also performs some NDIresearch, but it is not focused on corrosion.

The Laboratory uses eddy currentbecause it is a mainstream technique that isgood for detecting metal loss (while it alsodetects everything else). In addition, itworks in the presence of sealants and airgaps. The lab devotes approximately oneman-year annually to eddy current work,attempting to find ways to detect corrosionearlier, discriminate it from other defects,

and quantify the damage it causes. They aretrying to establish, in laboratory conditions,the minimum amount of corrosion which isdetectable by eddy current techniques. Todate, they have gotten to 0.5 percentequivalent thickness loss (the losses werenot uniform) in 0.5 mm thick plates of 2024aluminum. They also have looked at the useof eddy current to detect losses in dual-layerpanels. Here they have established athreshold below 20 percent loss in thesecond layer for 1 mm thick 2024 aluminum.

When queried whether once their eddycurrent techniques were moved from thelaboratory, how they would discriminatewhether the signal they had detected wascorrosion or something else, they stated thatthey would use a scanning system (such asthe ANDSCAN from Krautkramer) whichwould allow the eye and brain of thetechnician/user to correlate the findings andseparate corrosion from stiffeners or rivetholes.

One scientist admitted that the use ofeddy current in thicker structures is more ofa problem since penetration is difficult. Herethey use pulsed or transient eddy currenttechniques. He has examined thesetechniques to detect material loss in multiplesheets of 0.9 mm thick aluminum alloy,using long period/delayed returns to makethe measurements. They have shown thatthe transient eddy current technique is ableto quantify the total percentage material lossin a multilayer structure, whilstsimultaneously discriminating signals due toactual material loss from unwanted signalsdue to variations in the air gaps between thelayers or changes in the probe liftoff.However, the theory is not fully developedfor more complicated structures and work on


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identifying the relevant relations isunderway.

AMRL is also conducting research inultrasonics, both laser- and piezoelectric-based. Their work concentrates on usingultrasonic techniques to detect early stagesof corrosion hidden underneath the top layerof a multi-layered aircraft structure. Theyemploy lamb wave technology to look atattenuation of these waves caused by theexistence of corrosion byproducts betweentwo externally mounted transducers. Theamplitude of lamb waves decreases withcorrosion layer thickness before thecorrosion results in significant pitting. Thus,their work focuses on measuring thethickness of the corrosion layer, rather thanon measuring the loss of good material, as ineddy current techniques, and is a promisingtool for early detection rather thanquantification of corrosion.

The NDE researcher involved in the lab’sultrasonic work stated that this single-layertechnique has potential but that sensitivityand ultrasonic transducer frequency dependson skin thickness, and presence of paint (orother) layers. Difficulties arise if the skinthickness tapers or if the number of coats ofpaint change within an inspection area, andseparate monitoring of these parameterswould be necessary for practical applicationof the technique. They have been able todetect down to 10 percent (50 microns)corrosion product thickness relating to 1percent (5 microns) material thickness losson a 0.5 mm thick plate. They also havebeen able to detect down to 10 percentcorrosion on a 1.0 mm thick plate, or 100microns of corrosion product, so clearly thetechnique loses sensitivity as plate thicknessincreases. In addition, they have been able toseparate the transducers by only 40 mm on

painted surfaces and 60-100 mm onunpainted surfaces, limiting the large-areascanning capabilities of the technique todate.

This Lamb-wave work is now in thereporting stage and present active corrosion-related research is presently concentrated onthe detection of moisture and disbonds inhoneycomb structure. The techniques beingevaluated for this purpose in the NDEresearch areas are more quantitative use ofthe Bondmaster (linked to ANDSCAN for2-D data presentation for ease ofinterpretation), acousto-ultrasonics andAirbus Elasticity checker.

They plan to examine the use ofultrasonics in honeycomb structures in thenext phase of their analysis.

The division representatives stated thatthey see no real impediment to theintroduction of new NDI technologies. OnceAMRL (the R&D support laboratory) canconvince the Services of the value of a newtechnology, it can be introduced and used.Thus, AMRL has a strong input to theADF.

The DSTO representatives from theFatigue and Fracture Detection andAssessment Section, Aeronautical andMaritime Research Laboratory alsodiscussed their corrosion sensing work. Thegoal here is to detect corrosion as early aspossible, especially in corrosion-prone areasof aircraft. They are examining the use ofinstalled sensors, such as fiber optic sensorsembedded in the sealant of lap joints. Theyare searching compounds for a fiber coatingwhich will allow them to use fluorescence todetect corrosion at the lowest possible limitof detection. At present, they have gotten to0.2 ppm of corrosion. Essentially, they


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exploit the propensity of evanescentradiation to escape from the core of anoptical fiber by attaching a strobing lightsource to one end of an embedded fiber and asensor to the other. The team de-clads thefiber in the potential area of corrosion,recoating it with a special coating thatfluoresces in the presence of corrosionproducts. When the fluorescent light re-enters the fiber, it can be detecteddownstream.

In addition, they are examining the use ofsheets of conducting polymers to inspecthidden joints inside airframes, relying on achange in the properties of the polymer toreveal corrosion or water contamination. Forexample, if moisture ingresses near thepolymer sheet, a measurable decrease in theconduction of the sheet will occur or thepolymer might change color. The latter canbe incorporated into clear sealants aroundfasteners: if the sealant breaks down, thecolor change can be seen by a simple visualinspection. One representative noted thatDr. Agarwala of NAWC is doing similarwork with chemicals in paint coatings.

The Fatigue and Fracture Detection andAssessment Group discussed their work inthe NDI of honeycomb structures, includingfailure analysis, accident investigations andfatigue research. They take an engineeringapproach to fatigue analysis, considering thematerials involved, and use NDI for theirstudies. They also provide consultantsupport to the RAAF, both in satisfyinglonger term research needs and by writingprocedures.

They stated that the structural integrityaspect of corrosion is a big issue at present.While there is a need to both stop corrosionand control it, it also is important to assessthe short-term criticality of any corrosion

that has been detected to an aircraft’sstructural integrity. Thus, they feel theirwork has more practical applications and isless physics-based and research-orientedthan the work done in other areas of AMRL.They focus on real aircraft components andnear-term solutions. For example, they arestudying failure and cracking problemsexperienced in F/A-18 trailing edge flaps.Their lab does develop some technology:they developed depth C-scan techniques toexamine impact damage to compositestructures on the F/A-18. However, sincethey have had some bad experiences in thearea of technology transfer andcommercialization, they never went anyfarther with the technology and did notattempt to develop it to a point to which itcould be deployed to a RAAF unit.

The Ship Structures and MaterialsDivision (SSMD), Aeronautical andMaritime Research Laboratory, is examiningthe use of electro-chemistry for corrosiondetection. The goal of their work is tomeasure the corrosion itself or the presenceof the aggressive chemical species whichcause corrosion. They use a galvanic sensorto detect moisture but interpreting this dataand correlating it to the rate of inducedcorrosion is key. To do this, they useairframe materials as their sensors, and areconducting tests to force corrosion to occurso that they can measure the resultantchanges to current and resistance. It is hopedthat this will allow potential corrosion to bedetected before it can begin. The division’ssecond area of study is to use changes inelectro-chemical impedance to check theintegrity of coatings. Each pinhole-sizedbreach of a coating reduces the impedance ofthat coating. That property can be used tomonitor the condition of the coating. They


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are targeting their work to the areas aroundfasteners.

Representatives of the Airframes andEngineering Division (AED) then talkedabout their work providing NDI support tothe RAAF. They do not devote much studyto examining classic corrosion of lap joints,preferring to look at the implications ofcorrosion on the structural integrity of anaircraft. They mentioned the use ofthermography to examine F-111 overwingfairings and accident investigations. TheAED has two thermography systems, oneoperating in the 3 -5 micron band and theother in the 8 -12 micron band.

The AED representatives stated that inP-3C elevator skins, the 10 percentacceptable corrosion threshold is OEM-mandated. They said second layer corrosionis the hardest NDI problem. Their lab haslooked at acoustic emission techniques, buthave not had consistently successful results,so they are placing more emphasis onthermography now. Eddy current techniquesare used for countersunk fasteners with verysmall holes.

Their first work on composites involvedflash thermography. Image enhancementtechniques were employed to bring out moredetail and even heating pads were used to getthermographic images through the compositehoneycomb.

NDI of the honeycomb structure of theF-111 also is of great interest, especially lifeextension of the existing structure. One AEDrepresentative said the aluminum core withaluminum skin honeycomb structure of theF-111 made thermography difficult sincethere is no change in resistance between thecore and the skin. (In contrast, he said theF/A-18 has a composite over a phenolic

core). He mentioned that dual-band infra-redtechniques might help here. He is evaluatingthe value of thermal tomography and theGalileo high resolution system for examininghoneycomb structures.

The AED representative said thatproblems with honeycomb structuresinclude water ingress, corrosion, skin/coredisbond/degradation and problems with thenode bonds. Potential NDI methods used tostudy these problems include conventionalNDI methods (such as ultrasonics, eddycurrent, radiography, dye penetrants, et al.),thermography, ComScan (Comptonbackscatter x-ray), neutron radiography (butonly over small areas), D-Sight and advancedultrasonics.

He menti oned that work is be ing d oneby CSIRO at L indfi eld ( near Sydne y)und er co ntrac t wit h Boe ing l ookin g atalu minum core /comp osite skin hone ycomb and trav eling wave s to scan over thesur face of th e tes t art icle; this meth od ca npic k up disbo nds o n bot h sid es of the skinand can ident ify o n whi ch si de th e pro blemocc urs.

He said the honeycomb structuresexperience the three types of problems alsodiscussed at RAAF Amberley (see Section5.2.4.4): skin-core disbond, node bondfailures (the separation of the nodes in thehoneycomb), and fillet bond failures. Thelatter is the greatest problem, since it is hardto detect these failures, they can be critical(there is at least one case of the in-flight lossof a control surface made of honeycomb),access to many problem areas is difficult, itis believed that some of the panels whichcould suffer from this problem may have nomargin of safety/tolerance for this type offailure, and it is impossible to replacesome/many of the affected structures since


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they are integral to the aircraft. His lab andothers are “throwing everything at them [i.e.,the failure modes] that we can think of.”

He then discu ssed ComSc an te chniq uesdev elope d by Phili ps Co mpany . Phi lipshas a sy stem avail able comme rcial ly at acos t of about $900 K AUD , but it r equir esa l arge numbe r of detec tors if it is t o befas t eno ugh t o be usefu l in a pra ctica lenv ironm ent. ComSc an te chniq ues c an gi vedep th in forma tion; howe ver, a new det ectio n hea d (an d re- scann ing o f an area) is neede d for each targ et de pth i n the test art icle. Acce ss to only one side of th estr uctur e is neede d, bu t the hard ware mustbe locat ed cl ose t o the surf ace a nd th e siz eof the h ead p rohib its a ccess to t ight space sand big protr usion s on the s urfac e its elffor ce to o muc h lif t off . Ben efits ofCom Scan inclu de it s cap abili ty to prov idelar ge ar ea, n on-co ntact scan ning, its singl e-sid ed na ture, its non-r elian ce on film , and its capa bilit y to permi t 3-d imens ional rec onstr uctio n (as many as 2 2 sep arate dep th sl ices have been produ ced). How ever, it i s exp ensiv e, ha s onl y lim itedpen etrat ion c apabi lity (sinc e it relie s ondet ectio n of backs catte r rad iatio n), i tsres oluti on de creas es as pene trati oninc rease s, an d it prese nts a n ion izing rad iatio n haz ard.

In summary, the AED representativeagreed that there are no magic bullets in thearea of NDI of honeycomb structures. Hesees the possibilities for some short-termincremental advances in the areas of small-size ultrasonics probes, use of eddy currentin rivet holes, and better penetrant/etchantmethods. In the long term, he sees potentialbenefits from/uses of Compton scatterimaging, pulsed eddy current, non-contactultrasonics and thermography for simple

geometries. He personally is going to pursuethermography.

In a final note, the scientist discussedcorrosion problems in helicopters and theirrotors. While he is aware that there areproblems with these structures, hepersonally does not study them in his labsince visual inspection and replacement isused to handle any/all problems in the field.For example, the rotors are discarded sofrequently for other reasons (for example,H-60 Blackhawk rotors are pressurized andonce the pressure is lost – indicating thepossible existence of a crack – the blade isdiscarded), that corrosion rarely is aproblem. He also mentioned that since theRAAF relies on OEM specifications,AMRL only sees out-of-the-ordinaryproblems.

Regarding information availability, oneDSTO representative mentioned that noneof the research/papers get to Australia, andespecially to the RAAF bases.

One representative said that he believedthe USN at Jacksonville records all corrosioninformation for its P-3s and that the USAFrecords similar data for its aircraft at Warner-Robbins AFB. He indicated that the RAAFat Edinburgh in South Australia does keepinformation on corrosion work costs as well.

A representative commented that hebelieves there is economic incentive for themilitary to improve its ability to detectcorrosion. He asserted that it is cheaper tofix it if it is detected early.

5.2.4.2 RAAF RichmondRAAF Richmond is responsible for the

depot-level maintenance of Australia’s P-3and C-130 aircraft, as well as a small numberof Boeing 707s used for VIP travel.


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The major techniques used in their workare eddy current and ultrasonics, usingequipment such as the Panametric Epoch III,Zetec MIZ-22 and Elotest B1 equipment.Richmond has no imaging equipment,performs no fusion of data from multipletechnologies, and does not usethermography. It does have an x-ray facility.Ultrasonic techniques are used for corrosiondetection, but only for single layer corrosion.RAAF personnel said that, with the digitalultrasonic equipment used at Richmond, theextent of corrosion is sometimesoverestimated due to ringing in the probe.Eddy current is used primarily to detectstructural defects/cracks (especially aftergrinding out corrosion), but is also usedextensively for corrosion detection in holes.

Hawker Pacific performs contractmaintenance of the P-3 aircraft for bothAustralia and New Zealand at Richmond.Work for the RNZAF focused on wingreplacement due to fatigue and horizontalstabilizer corrosion in the 7075-T6aluminum used in that structure. RAAF hashad to refurbish a number of engine nacelleson the New Zealand aircraft, due to thegreater weight of that aircraft (compared tothe Australian variants). New Zealand’sP-3s were experiencing more problems withcorrosion than were Australia’s. In fact,while it is not official policy, the life ofRNZAF P-3 wings are limited by corrosionrather than fatigue.

The RAAF P-3s have experiencedsignificant corrosion problems in the pastbut many of these problems are now beingmanaged by the application of waterdisplacing chemical preservatives topassivate the corrosion. One of the problemareas has been in the aft wing spar. HawkerPacific uses eddy current and ultrasonics to

examine every fastener in the spar caps,requiring a huge expenditure of man-hours.Hawker Pacific personnel were unaware ofany realistic robotic means to perform theseinspections, given the complexity of thestructures inspected.

Lit tle w ork h as be en do ne so far oncom posit e pat ches on th e Aus trali an P-3s. Bon ded m etal repai rs ha ve be en us ed on C-130 stab ilize rs an d, wh ile o nly i n the ear ly ch eck-o ut st age, seem to be per formi ng we ll.

Squadron personnel pointed out thatthey believed the 10 percent “rule of thumb”threshold for repairing a corroded body partwas inappropriate because any “acceptable”level of corrosion would depend on both thestresses and the original thickness (i.e., thedegree of over-engineering) of the panel/body part in question.

5.2.4.3 Tactical Fighter LogisticsManagement (TFLM) Squadron, RAAFWilliamtown

RAAF Williamtown is the home base of71 F/A-18 aircraft (with an average age of 10years) assigned to three flying squadrons.These squadrons are supported by the 481Squadron, a maintenance squadron/facilityalso located at Williamtown. The TFLMSquadron is the engineering authority forF/A-18 maintenance, managing repairs,acting as a central logistics facility, andapproving and promulgating maintenanceprocedures.

All maintenance at Williamtown is doneby RAAF personnel (either in the flyingsquadrons or in the 481 Squadron) and allwas classified as being operational-levelmaintenance. This includes an R-2 servicingof the aircraft which is performed every 250flight hours (approximately 18 - 24 months)


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and which takes 30 - 40 days. (Each flyingsquadron does six R-2 inspections per year,while 481 Squadron does 12 annually).

RAAF Wiliamtown has considerableNDI equipment (ultrasonic, radiography,magnetic particle, eddy current) which ismainly applied for crack detection in metalliccomponents and comosite monitoring. Atpresent, visual inspections are the “primary”corrosion detection technique used by theTFLM Squadron, although 481 Squadrondoes also carryout some eddy current workfor corrosion. Visual searches also are usedto search for impact damage in compositestructures.

Williamtown’s F/A-18s have experiencedsurface corrosion due to its near-sea location.While some corrosion problems have beenseen in fastener holes, it rarely has extendeddeep into the surface. Although it was statedthat the emphasis placed on corrosiondetection has dropped off in the last severalyears, whenever corrosion is detected,operating procedures mandate that it mustbe removed. However, it is not clear that allthe corrosion found is reported to theTFLM Squadron: despite the length of theR-2 inspection, it was admitted that theaircraft occasionally complete theinspection/scheduled maintenance withoutthe elimination of all corrosion, due to thepush to move the aircraft through theinspection. Grinding is used to removeidentified corrosion.

The R-2 procedure sees metal corrosionas well as the delamination of the aircraft’scarbon composite structure. A future NDIsurvey is planned for the honeycombstructure.

RAAF personnel stated that they werenot confident that they were finding all the

corrosion resident in their aircraft. It wasmentioned that the Canadians have subjected15 - 20 of their F/A-18s to an aircraftstructural integrity (ASI) inspection, whilethe Australians have performed only one. Astudy was done to justify depot servicing tocheck for corrosion, but it was found to betoo costly ($20M AUD per aircraft) to becost-effective. This was particularly thecase given that other nations (e.g., the U.S.Navy) operate their F-18s in much morerugged conditions than Australia andinternational cooperative programs routinelyfive Australia advance notice of likelycorrosion locations in the R-18s.

RAAF personnel stated that one of themajor requirements which is currently beingaddressed is for a datahandling/recording/storage system to identifyand map out corrosion “hot spots” and tomanage the information on where corrosionis likely to be found on the airframe. Since itis expected that Australia will maintain itsF/A-18s in service until at least 2020 - 2025,corrosion detection was viewed as a concernof increasing importance, although it wasadmitted that no real corrective program forcorrosion presently exists. However, plansare in place for a “bird bath” system toimprove aircraft washing and considerationis being given to increased use of WDCPs.At present, the preventative measure takeninclude: 1) washing the aircraft every 60days, although this was admitted not to befrequent enough; 2) use of WDCPs (e.g.,LPS-2 and -3); 3) removal of EMI dissimilarmaterial connections; and 4) use of improvedpaint (semi-gloss vice matt, although it wasstated that the aircraft have not been paintedas often as would be liked).

They also stated that it would be verydesirable to detect corrosion without the


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need to dismantle significant parts of theaircraft (a major driver of the $20MAUD/aircraft cost of a depot-level corrosiondetection regime). In this context, external orone-sided corrosion detection sensors wouldbe of maximum desirability.

RAAF personnel pointed out that the 10percent “rule” is not generally applied.Instead, more interest is placed on thecriticality of the specific component and onhow much material is left in a corroded area,rather than on how much has been lost. Thedesire for a corrosion monitoring andreporting system to map problem areas wasrepeated, so that the loop can be closed onthe problem and the prevention of corrosion(e.g., the WDCPs) can be attempted, insteadof just reacting to its presence.

Williamtown RAAF personneldemonstrated the use of “metallic rubber” tocheck for internal cracks and corrosion. Thisis a rubberized compound drawn by amagnetic field into the internal surfaces of acomponent being tested. When dried andextracted, a simple visual inspection of the“mold” permits the detection of cracks andcorrosion. The material is manufactured byDynamold, Inc. of Fort Worth, TX, and hasa NSN code number assigned. Theyindicated that it is not appropriate for use inaluminum structures.

5.2.4.4 RAAF Amberley,Queensland

RAAF Amberley is the home of 501Wing, which is responsible for performingdepot-level maintenance on all of Australia’s(and now the world’s) F-111, relying on theoriginal equipment manufacturers (OEM),but modifying the OEM procedures for localconditions. Routine maintenance at 501Wing is now being part-civilianized in aneffort to cut costs.

Amberley is also the home of Australia’sNon-Destructive Inspection StandardsLaboratory (NDISL). This group has a lowbudget and a small NDI team. This teamtrains and reviews RAAF inspectionpersonnel for all RAAF bases and also trainsdefence staff from Southeast Asia. Theymake their own reference standard pieces tocheck their NDI equipment and to traininspection personnel. This team is alsoresponsible for writing NDI procedures forRAAF aircraft maintenance.

Visual inspection is the primarycorrosion detection technique used atAmberley. However, the NDISL had justreceived a new NDI instrument, a SonicBondmaster. This uses lower frequencyultrasonics to check for disbonds, and isuseful in finding crushed core or waterintrusion in honeycomb structures. Othertechniques used include X-rays, ultrasonics,eddy current inspection and magnetic rubberinspection.

At the F-111 maintenance facility, staffassigned to maintain those aircraft statedthat Australia is now the world’s sole userof the aging F-111. The 22 originalAustralian F-111Cs average 25 years ofservice; the 16 F-111Gs recently receivedfrom the USAF are somewhat younger. Allare expected to remain in service for another25 to 30 years.

The NDI lab primarily inspects controlsurfaces (honeycomb structures/panels). Allother corrosion inspection is performed viavisual means, and corrosion is treated on thespot by grinding/rubbing it out, often byhand. In fact, it was stated that a majormeans of detecting corrosion in body panelswas to conduct a tap test in whichmaintenance personnel crawl over theaircraft tapping it with hammers to detect


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(aurally) areas for more detailed subsequenttesting. Such a manual test takes from 5 to 6days of effort by multiple personnel tocomplete.

Steel structures on the aircraft can beinspected using magnetic rubber (discussedpreviously) to find defects on the order of.010 - .020 cm in size. Radiography is used,but it was stated that it is not good at findingearly corrosion and the parts/aircraft beinginspected must be moved to a separatefacility. Thermography had been used withonly limited success: the available equipmentis old and past failures/inadequacies havelimited its acceptance and use.

Personnel stated that stress corrosion isa big problem with these aircraft, especiallyon the floor trusses of the crew module.These trusses are difficult to reach andinspect, requiring the removal of the crewseats and other equipment. Boron patcheshave been used to make required repairs. Inaddition, the splice joint on the overwingfairing has been “letting go.” The D6 steelhoneycomb generally has not presented aslarge a corrosion problem as had been feared(given USAF experience with the aircraft),despite the relatively humid and tropicalclimate of Amberley. Problems have arisenwhere the cadmium plating has been chippedoff, however. In addition, the D6 steel hasexperienced cracking problems, mostly in thewing carriage boxes.

The F-111 possesses many skin-to-honeycomb contact areas and staff pointedout that many of these areas are not or cannot be inspected. Problems have been seenon the dorsal surfaces of the aircraft (wheremaintenance personnel tend to walk), butrarely are these areas inspected by anythingother than the previously mentioned taptest. They also mentioned that the smoke

from the starter carts has corroded the doorsnear the engine starter ports. Corrosion hasbeen detected on the bulkhead behind theradar dish, and is removed by hand buffing.The forward equipment bay doors alsoexperience corrosion, and not just at thehinges.

The depot personnel mentioned thatcorrosion in the engine intakes is being seenwith more frequency. Some believe that thishas been maintenance-induced, i.e., that theact of stripping the paint off the inlets tosearch for and remove corrosion has inducedthe problem to grow in magnitude, sincemore corrosion was seen with each strippingand inspection. The response has been tocease the stripping of the paint in the engineintakes. This would appear to be a ripeopportunity for the use of non-visual NDItechniques to search for corrosion beneaththe non-removed paint in this area.

No use is made of WDCPs at Amberley.Only WD-40 (a water displacementformulation) is used as a lubricant. Machineoil is sprayed into finger tanks (which are nolonger used to carry fuel on the Australianaircraft) to act as a corrosion preventative.

A major inspection of the aircraft, calledan R-5, is performed every 2,000 flighthours, or approximately every 7 years. Thisinspection takes from 30 - 40 weeks; theduration is dictated by the availability ofspares.

Data is collected pertaining to themaintenance performed on each aircraft, butnone is related explicitly to the cost ofdetecting and eliminating or preventingcorrosion. It was estimated that from 30 to40 percent of the work performed on theF-111s is corrosion removal.


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Depot personnel discussed Fillet Bondand Node Bond Problems in Bonded Panels(particularly honeycomb structures). Threetypes of problems have been seen inhoneycomb structures. The first is skin-to-core disbonding, a standard problem inwhich, as its name implies, an aircraft’s skinpanels separate from the honeycombstructure beneath them. This problem can berelatively easy to detect with such simpleNDI techniques as a tap test.

The second is fillet bond failure, which isinterfacial failure between the honeycombcore and the adhesive. The problem isdifficult to detect. With aluminum orgraphite skins, common tap tests areinadequate (since loads and stresses on thepanels often change when the aircraft is onthe ground vice in flight), and even ultrasonictechniques are somewhat ineffective(although thermography might work). Inaddition, large areas often need to bechecked: in one example, staff stated that theproblem area was 20 times larger than thesize of the problem which had beenidentified originally by a tap test.

Fillet bond failures can result in a greatloss of structural strength. They are almostinvariably associated with moistureintrusion, caused by problems such as failedsealant at fasteners, disbonds, or defective(usually injection) repairs. It also issuspected that water may be migratingthrough graphite seams. While corrosion isoften present, it is not the cause of thefailures. When the failures get bad enough,the skin surface of the affected area can (andhas) blown off in flight. These types offailures have been seen in F/A -18A to Daircraft with F/A-18D models less than fiveyears old, and in the F-111. Representativesstated that even the Airbus 320, with its

phenolic core honeycomb, has experiencedthese problems.

The t hird type of failure is node b ondfailu re, in whi ch the bon d which is suppo sed to kee p together the cell walls ofthe h oneycomb i tself fall s apart. T his typeof fa ilure, whi le easily detected b y x-rays,is ge nerally fo und only d uring repa ir of thestruc ture for o ther reaso ns. In fac t, while i tis ge nerally ca used by th e elevated tempe ratures us ed during otherrepai r/curing p rocedures, this type offailu re may occ ur at a lo cation awa y fromthe s ite of the repair wh ich caused it. Nodebond failures c an result in a core cell peelstren gth loss o f up to 90 percent.

Depot representatives also stated thatthe F-111 horizontal stabilizer has been aproblem. If/when the Sacramento AirLogistics Center closes, Australia, whichplans to keep their F-111s operational untilat least 2020, may find it difficult/impossibleto repair those structures.

Depot representatives stated that themaintenance procedures promulgated by 501Wing take what the OEM recommends and,whenever they are found to be wanting,tailors them for the local/Australiansituation. They noted that 501 Wing has theauthority to make decisions on the need toprocure a new piece of NDI equipment,based on needs expressed by the flyingsquadrons. However, since funding isalways a problem, whenever theydevelop/get a new procedure to perform,they try to build around and employ anexisting piece of NDI equipment. In theinstances when money becomes availabledue to the cancellation of other projects, 501Wing can buy new equipment with thosefunds. However, even when 501 Wing canprocure new NDI systems, training on their


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use is difficult to get (due to Australia’sdistance from the manufacturers) and then itis difficult to find the funding to travel anduse the equipment at any location other thanAmberley. Thus, it is difficult to “buy andtry” a new system.

The depot representatives could notthink of a corrosion-caused failure. Whereasthe F-111s used a great deal of sealant ontheir panel joints, the newer helicopters inthe Australian inventory were manufacturedusing dry joints, and have experienced manycorrosion problems. Because of this,corrosion is receiving more attention nowthan it has in the past.

5.3Department of Transportation

The Department of Transportation isinvolved in a number of different R&Dprograms for detecting corrosion in aircraft.The following paragraphs highlight some oftheir activities in this area.

5.3.1 FAA Technical CenterThe F AA Technic al Center initiated a

progr am in insp ection sys tem resear ch in1990 as part of the Natio nal Aging AircraftResea rch Progra m. That pr ogram wasdesig ned to imp lement Nat ional Traf ficSafet y Board re commendati ons in rep ortAAR 8 9/03, whic h recommen ded that t heFAA p erform res earch to s upport the deplo yment of m ore capabl e inspecti onsyste ms with le ss sensiti vity to hu maninade quacies. G overnment and indust ryovers ight of in spection r esearch fu rtherrecom mended tha t the FAA establish avalid ation cent er to ensu re the rel iability o fnew t echnology being intr oduced int o themaint enance env ironment. To accompl ishthis, the FAA s et up the Center for Aviat ion System Reliabili ty (CASR) at

Iowa State Univ ersity to oversee in spectionsyste m developm ent and th e Aging Ai rcraftNonde structive Inspection SystemValid ation Cent er at Sand ia Nationa l tocondu ct inspect ion system validatio ns. TheFAA d oes not co nduct any research i n-house .

Like the U.S. Air Force, the FAA doesnot consider corrosion a safety issue. Theydo not consider corrosion a problem. Rather,they define it more as a cost issue.

The performance standards that theFAA is trying to achieve are:

• Detection of 0.025 inch crackemanating from the shank of a countersunk rivet hole in 40 mil fuselage skins

• Detection of 0.050 inch crackemanating from the shank of a rivet holein the second and third layers of fuselageskins (40-60 mills below surface)

• Detection of a 0.100 inch crack under0.500 inches of aluminum wing skin

• Reliable detection and mapping ofcorrosion thinning to five percentmaterial loss

• Reliable detection of one square inchdisbonds in composites up to five layersfrom the inspection surface.

The FAA works with CASR to developnew maintenance procedures where theemerging technologies that complement themedium to heavy airline inspections aregiven their first exposure for potential useby an airline. The new technology ortechnique then becomes an issue for theairlines to either convince and/or pay for themanufacturer to authorize the technology.This is because the manufacturer ultimatelycarries the liability. The manufacturer takes


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an existing service bulletin and submitsliterature on the technology along withservice literature. The FAA then reviewsthis application and, if approved, issues anAD. Oftentimes, operators request analternate means of compliance that appliesonly to that operator. This alternate can begranted in a shorter period of time.

FAA representatives stated that airlinesprimarily rely on visual inspections,believing that there is always some sort ofvisual indicator of corrosion and that, oncediscovered, then needs to be inspectedfurther to determine the extent of theproblem. The FAA representatives statedthat the ultrasonics techniques are not thatpopular with the airline industry due to therequirement for a water medium to couplethe article and the transducer. He noted thatthe FAA is most interested in the scannedpulsed eddy current techniques and theyhave a parallel effort to the USAF in thisarea. The FAA feels that this technique hasmuch to offer in its specific area of interest -the detailed inspection or point detection ofcorrosion in a small area.

The FAA repre senta tives poin ted o uttha t the FAA’ s man date is no t dir ectiv e bynat ure a nd th us, t hey w ill n ot im posecor rosio n det ectio n tec hniqu es an dequ ipmen t on eithe r the airl ines or th eman ufact urers . Ins tead, they enco urage theair lines to f ollow what ever guida nce t heOEM s dic tate regar ding maint enanc e. As iscur rentl y don e, th e ind ividu al ai rline s wil lcon tinue to w ork w ith t he ma nufac turer sto emplo y equ ipmen t and tech nique swhi ch pr ove c ost e ffect ive a nd wh ich m eetthe insp ectio n nee ds in achi eving com plian ce.

The FAA’s inspection systemdevelopment work embodies several relatedefforts to advance flaw detection technology:

• Crack Detection: To improve thesensitivity and reliability of techniquesto detect and characterize small, inter-layer, and obscured cracks characteristicof widespread fatigue damage.Technologies currently of interest to theFAA include laser ultrasonics, pulsededdy current, superconducting quantuminterference devices (SQUID), ultrasonicpulse compression, energy sensitive X-ray for engine case inspection, dualprobe ultrasonics, electromagneticacoustic transducers, and advancedelectromagnetic sensors for widespreadfatigue damage assessment, and anadvanced penetrant inspectiontechnology.

• Corrosion Detection: To developnon-invasive techniques to detect andcharacterize disbonding andunderstrength bonds in skin splices.Technologies of current interest forverifying bond integrity includethermography, low frequency ultrasonicscanning, air coupled ultrasonics, andcapacitive array sensors (for inspectionof composites). Corrosion detectiontechnologies of interest include magneto-optic eddy current imaging (MOI),pulsed eddy current, D-Sight, andportable low-radiation hazard, real-timex-ray.

• Robotics and Automation: Toenhance the capability and reliability ofinspection systems by developing faster,more accurate means of deploying theprobes and interpreting probe signals.Technologies of current interest include


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signal processing for sliding and rotatingeddy current probes, self-focusingultrasonics, and signal processing forultrasonic billet inspection.

The technologies that the FAA has andis studying and the programs they have inplace to conduct this research is highlightedin the following paragraphs.

One of the FAA sponsored programs isto provide new technology for crackdetection based on non-contact generationand detection of high frequency ultrasound.The Sagnac interferometer for ultrasoundmeasurements has been developed. A fullyfeatured interferometer will be tested onrough aircraft surfaces under field conditions.CASR is working on the development of thisprototype.

The FAA has also sponsored CASR todevelop pulsed eddy current inspectiontechniques to detect and characterize smallfatigue cracks in layered joints. This taskbuilds on a swept-frequency devicedeveloped at ISU that can determine thelocation of corrosion loss, thickness of bothouter and inner layers of skin, and separationbetween the two layers. The technology hasbeen licensed by Sierra Matrix.

In addition, CASR is working ondeveloping scanned eddy current methods todetect and characterize corrosion andcorrosion related cracking in lap joints,quantitatively determining metal skinthickness loss. A laboratory pulsed eddycurrent device has been developed and asecond generation prototype has beendesigned. This project will further developand integrate pulsed eddy current technologyinto a portable scanning instrument.

SQM Technology is working withCASR on another eddy current technology

project to extend this technology to deepinspection for hidden flaws. They plan tobuild a prototype superconducting quantuminterference device (SQUID) for deep pulsededdy current inspection of thick wingstructures by January 1999.

CASR, in conjunction with NorthwesternUniversity, is also working to develop a dualprobe ultrasonics system for the detection andcharacterization of fatigue and stress corrosioncracks in multi-layered structures. At thistime, the DC-9 T-Cap applications iscomplete, has been approved and is beingapplied by at least three airlines. Validationefforts are underway for the DC-9 Wing RearSpar Aft Flange and the DC-10 No. 2 EnginePylon Spar Cap Strap in cooperation withNorthwest Airlines and McDonnell Douglas.

CASR is working on the development ofa portable low-radiation hazard X-raysystem capable of providing enhanced real-time X-ray images coupled with a detailedquantitative measure of material thicknessand the presence of corrosion at selectedpoints of interest. They plan to completethe experimental characterization of thediffraction effects in samples supplied byPratt and Whitney and Boeing using thegermanium or the CdTeZn detector anddevelop specifications for the system.

CASR has contracted with Wayne StateUniversity to provide thermal wave imagingtechnology for rapid integrity assessment ofadhesively bonded aircraft structures withemphasis on detecting corrosion anddisbonding in multi-layer joints. To date, thepulse-echo thermal wave inspection systemhas been demonstrated in the laboratory,during field trials at Northwest Airlines, andin conjunction with an USAF corrosiondetection program. Several tests have alsobeen conducted at the AANC and a reduced


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size imaging system has been developed.They are working on an advanced prototypethat will offer more practical use with littleor no aircraft preparation required.

This technology also has strong USAFsponsorship. NASA Langley is interested inthis technology as well. NASA is fundingBell Scientific in the area of algorithmdevelopment at the Lawrence LivermoreLaboratory to help refine this currenttechnology process.

CASR is also exploring the feasibility,applicability, development, andimprovement of air-coupled ultrasonicinspection methods for defect detection intypical aircraft geometries, particularlyconcentrating on composite materials andcomposite joints. McDonnell Douglas hasinterest in this technology and has suppliedcoupons to be tested.

In addit ion, CASR has j ust s tarte dexp lorin g app licat ions of no velele ctrom agnet ic in spect ion m ethod s bas edon rapid -scan , sta ring/ focus ing c apaci tivearr ay se nsors to N DE an d NDI ofcom posit e mat erial s. A feasi bilit y stu dy is und erway .

CASR is concentrating resources ondeveloping a low frequency immersionquality ultrasonic scanning method using adripless bubbler to detect corrosion anddisbonds in adhesively bonded structures.The dripless bubbler was demonstrated atthe AANC in April and November 1994.The system was tested in February 1995during Tinker AFB tests. Sierra Matrixlicensed the technology in 1996 and isactively developing a commercial system.

CASR is in the process of developing asimplified version of a new ultrasonictechnique to detect small cracks, high

density inclusions, hard interstitial defects,and stress-induced porosity by usingadaptive time-delay focusing of either theoriginal signal or the time reversed scatteredsignal. The second generation fieldprototype with surface and lamb wavecapability is scheduled to by completed byNovember 1997 with validation forecast tobe completed by mid-year 1998.

CASR has also funded the Canadiancompany, Diffracto, in conjunction withTransport Canada and NRC, to develop aprototype D-Sight system for rapid surfacecorrosion assessment. A second generationprototype was completed in 1995.

CASR has been assessing the reliabilityof representative and critical visualinspection activities to identify and assesssome of the more important factors effectingsuch activities. The experimental trials arenow complete. They have producedquantitative results on the probability ofdifferent flaw/defect types and sizes, inter-inspector reliability, and an estimate ofinspector characteristics included in thedesign. Also documented are qualitativeresults comparing experimental “typical”situation with inspectors’ usual workingcontext, rank ordering and weighing theimportance of performance influencingfactors (including time factors) andclassifying errors.

Mature technologies are transitioned to avalidation and final development phaseunder the FAA’s inspection reliability andvalidation program. In regards to technologytransfer initiatives, the FAA isaccomplishing this through a process ofapplication oriented systems development,system validation, and informationdissemination, culminating in licenses andcommercialization partnerships. For


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example, in August 1996, CASR signed alicensing agreement with a manufacturer ofinspection equipment for two CASRdeveloped technologies: a pulsed eddycurrent device and an advanced ultrasonicinspection system.

Working together with the AANC,CASR has successfully transitioned a newinspection technology to industry. CASRdeveloped a prototype ultrasonic device,which was validated at AANC. It has beenspecified in a McDonnell Douglas ServiceBulletin as an alternate inspection techniquefor the DC-9 wing box T-cap inspection formandated corrosion detection inspection.The new technique will save over 700 man-hours per inspection compared to thecurrent inspection method. It also requiresless disassembly of the aircraft part toconduct the inspection, thus resulting in lesschance of ancillary damage during thedisassembly and reassembly if no corrosionis detected.

Even though the work the FAA has doneis extensive, the FAA representativespointed out that the development of newtechnologies that the airlines need will likelycome from the DoD. The FAA has no realpower in directing or changing inspectionprocedures. They noted that there is no realincentive for the airlines to implementinspection techniques that reduce inspectiontimes. This is because the airlines havescheduled times at which they bring theiraircrafts in for medium and heavy checks. Toshorten the timeframe for the maintenancefunction will not change how early theseaircraft get released because of the otherprocesses that are conducted during thattime. These other processes take a givenamount of time to perform and no quicker

way to perform these other procedures isforeseen in the near future.

5.3.2 FAA Airworthiness AssuranceNDI Validation Center (AANC)

The Airworthiness AssuranceNondestructive Inspection Validation Center(AANC) was founded by the FAA inresponse to the Aviation Safety Research actof 1988, which mandates that the FAA carryout research and develop technologies tohelp the aviation industry to 1) betterpredict the effects of design, maintenance,testing, wear and fatigue in the life of anaircraft; 2) develop methods for improvingaircraft maintenance technology andpractices including nondestructiveinspections; and 3) expand general long rangeresearch activities applicable to aviationsystems. The AANC validates NDItechnology, assesses the reliability of NDIapplications, provides quantitative reliabilitydata on the field application of inspectionand repair technologies, and performs otherprojects to support the FAA and aviationindustry. Prior to its inception, there was noformal process for validating NDItechnologies.

Sandia National Laboratories was fundedby the FAA in August 1991 to establish theValidation Center at AlbuquerqueInternational Airport. The center is locatedin a 24,000 spare foot hangar at the west endof the airport.

A 27-year-old Boeing 737 aircraft wasacquired as a test bed in October 1992 andthe Center began operating in February1993. McDonnell Douglas DC9 fuselagesections were acquired in 1993. The U.S.Coast Guard donated a Falcon HU25Aaircraft to the center in June 1994. Thecenter acquired a Fairchild Metro II


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commuter aircraft in 1995 as well. Inaddition, the AANC has a large collection ofaircraft structural test specimens withcharacterized flaws, some cut from aircraftand others built to aircraft structuralspecifications with built-in flaws.

AANC’s original mandate was tovalidate inspection technologies for agingaircraft applications. That validation processinvolves the assessment of the reliability ofinspection systems (including humanfactors) and an estimation of the costeffectiveness of those technologies. It assistsdevelopers with analysis and provides costbenefit feedback relative to time taken forsample analysis versus false alarm rate. Sinceits inception, the scope of AANC activitieshas broadened to include activities instructural integrity analysis, repairassessment, and composite structureassessment.

The FAA’s National Aging AircraftResearch Program is concerned that theincreasing age of aircraft and thecorresponding increase in inspection andinspection frequency could result in thereduced reliability of safety relatedinspections. The FAA is examiningtechnologies having less susceptibility tohuman and environmental factors to offsetthe increasing inspection burden and reducepossible collateral damage associated withdisassembly, reassembly, and modificationof airplane structures.

FAA representatives have cited as aconcern that in today’s competitiveenvironment, many aircraft operators feelcompelled to maintain older inspectionsystems rather than invest in new systemsand training. The FAA believes that, withoutintervention, the potential exists fortechnologies to remain “on the shelf”

because operators cannot afford the time andresources to pursue validation and reliabilityassessments necessary to assure themselves,aircraft manufacturers, and regulatoryauthorities of the applicability of thosetechnologies. The AANC addresses thisissue. To date, the AANC has conductedwell over 100 demonstrations of emergingtechnologies.

As a result of the validation process, ifthe AANC discovers that a particularsystem is both capable and reliable, the FAAwill allow its utilization as an alternatemeans of compliance for certain FAAAirworthiness Directives. These directivesoften originally require significantdisassembly and inspection or modificationof the structure.

When an airline operator or maintenancefacility wants the FAA to certify atechnology as an alternate means ofcompliance, they must first demonstrate thetechnology to the FAA. The FAA thenadopts and approves the technology. Often,the airlines go to regional FAA officers forcertification of new technologies. In fact,over time, regional offices have beenconsidered to be specialized in certain areas,such as commuters, helicopters or engines.

In citing accomplishments to date, theFAA representatives listed the followingcorrosion detection technologydevelopments:

DC-9 Tee Cap Inspection - the AANCworked with McDonnell Douglas Aircraft,Northwest Airlines, and SAIC Ultra Image tovalidate an ultrasonic inspection techniquedeveloped by Northwestern University forthe detection of corrosion and cracks in theDC-9 wing box tee cap. The technique, whichhas been written into a service bulletin


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revision, improves inspection area coverageby 2 to 1 and inspection time by a factor ofat least 10 to 1.

Ultrasonic/eddy current scanner survey -the AANC evaluated representativeultrasonic and eddy current scanner systemsfor use on aircraft by demonstrating systemson test specimens and full-scale aircraft.

Some other activities currently inprogress (with industry or outsideparticipants) include a visual inspectionreliability experiment with assessment ofvisual aids (ATA Inspection Network), DC9wing box inspection alternate means ofcompliance (Northwest Airlines, McDonnellDouglas, Northwestern University), halonbottle inspection (American Airlines), multi-layer airframe crack detection reliabilityexperiment (Boeing), boron-epoxy structuralreinforcement (Delta, Lockheed, TextronSpecialty Materials, Robins AFB), and smallcrack detection reliability experiment(Boeing, Technical Oversight Group onAging Aircraft).

5.3.3 U.S. Coast GuardAs with the DoD, the Coast Guard is

concerned with maintaining and operatingaircraft in an extremely corrosiveenvironment. Their aircraft are flying wellinto their design life as well and hence, theCoast Guard is concerned with reducingcorrosion degradation. Corrosion is afleetwide problem that is exhibited in allCoast Guard aircraft. The Coast Guard hasdeveloped a Process Guide to provideguidance for managing an effectiveAeronautical Engineering Corrosion ControlProgram. This guide establishes policies toreduce the impact of corrosion deteriorationon aircraft, components, and supportequipment; providing guidance for a written

air station corrosion control plan, andensuring that future systems are designed tobe corrosion resistant.

The Coast Guard has a CorrosionPrevention Advisory Board that providesrecommendations to the Chief, AeronauticalEngineering division regarding policy andoversight of the Coast Guard corrosionprevention and control program. In addition,the CPAB advises the Commanding Officer,Aircraft Repair and Supply Center, ofprocess improvements to enhance corrosionprevention and control at AR and SC.

The Aircraft Repair and Supply Center,Engineering Division, Corrosion Control andReliability Centered Maintenance Division,is working in conjunction with NAVAIR ontheir thin film galvanic sensor research for insitu corrosion monitoring. They haveoutfitted several H-65 helicopters with thesesensors in an effort to gather data on thelevels of corrosion experienced in theseaircraft. With this data, they hope to be ableto move towards condition basedmaintenance of their aircraft.

The sensor consists of gold and cadmiumplated on a Kapton film with carefully spacegaps. Wires lead to the data acquisitionsystem. When conditions provide enoughconductivity between the metal, a smallcorrosion current is developed which ismeasured by a Zero Resistance Ammeter.Up to eight channels can be monitored. Someare for the corrosion sensors; two are fortemperature/humidity probes. The data canbe downloaded to obtain a measure of thecorrosivity of the atmosphere in which thesensor is placed.

This project is being conducted as part ofthe Site Specific Aircraft Corrosion program.Sensors were placed on two aircraft at each of


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two air stations: Corpus Christi and Detroit.These stations represent the extremes ofcorrosive and least corrosive atmospheres. Byinstalling these corrosion monitoring units atthe air stations, they hope to be able toattribute that portion of the corrosion due tothe flight profile and that due to thegeographical location. If the results reflectdistinct differences between the two airstations, the team believes the data will enablePDM cycles to be selected on the basis ofcorrosion potential at each location, i.e.,prolonging the interval for those aircraft less atrisk.

5.4NASA Sponsored Activities

NASA has a number of distinctcorrosion problem areas where they areconcentrating much of their NDE R&Dwork. NASA Langley deals mainly instudying ways to detect and deal withcorrosion under a thin layer of aluminumthrough its Aging Aircraft program andcoordinates extensively with the Air Forcethrough its Aging Aircraft initiatives. TheKennedy Space Center research work, on theother hand, is aimed at studying corrosion ofvarious space systems and concentrates a lotof its energy in dealing with corrosion foundunder relatively thick aluminum and inbetween the tiles and the aluminum layer ofspacecraft.

5.4.1 NASA Langley Research CenterThe Nondestructive Evaluation Sciences

Branch at NASA Langley Research Center(LaRC) is one of the major drivers ofNASA’s NDE research program. Theprogram focuses on maintaining an NDEscience base core, developing newtechnologies for the Agency, and transferringproblem solutions to customers. The LaRCNDE research program is concentrated in

two Offices - Safety and Mission Quality(Code Q) and Aeronautics, Exploration andTechnology (Code R), covering applicationsprimarily for SpaceOperations/Transportation System(spacecraft integrity), Subsonic andHypersonic Aeronautics (aircraft integrity).

NASA Langley Research Center is thecentral focal point for the NASA sponsoredAging Aircraft Program and is working withU.S. Air Force NDE researchers at Wright-Patterson AFB on the Air Force StructuralIntegrity Program. The NASA AgingAircraft Program is a $45M program (total)that has been ongoing for seven years.

The general areas in which NASALangley NDE researchers are conductingresearch are thermography, ultrasonics, andeddy current. All principal investigators atNASA Langley performing the research inthese areas are NASA employees, of whichthere about 15. NASA NDE researchershave patents in thermography andultrasonics.

Specific technologies being researched atNASA Langley include understanding thephysics of thermography and ultrasonictechniques, and optimizing the techniques fortechnology transfer. The researchers believethat thermography is the best technique forthe overall scan of large areas such as thesurface of aircraft. They consider it a relativelyquick technique, taking eight hours to scan anentire B-737 aircraft. The researchers alsobelieve that ultrasonics and eddy current arethe best techniques for “point” inspections.Ultrasonics can detect material loss as low as 3percent; eddy current can detect material lossas low as 5 percent.

NASA staff stated that automation canalso help reduce costs and the time to


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perform corrosion inspections. NASA hassponsored an SBIR for a robotic crawler thatcan access hard to reach areas of aircraft.

5.4.2 Jet Propulsion LaboratoryThe JPL NDE and Advanced Actuators

(NDE-AA) Lab was established in May1991. The JPL NDE Lab supports the JPL’smaterials and structures NDE requirements,particularly space-flight hardware. The Labis involved with research and developmentto allow:

• Detection and characterization of defects

• Determination of material properties

• Sensors for in-process and in-service monitoring

• Characterization of actuators and sensorsat controlled conditions

The NDE-AA Lab current research areasinclude:

• Aging Aircraft NDE - Ultrasonicdetection and characterization of damageto metallic structures and degradation incomposite materials. This effort issponsored by AFOSR and is asubcontract with the University of Texasat El Paso (UTEP) The leaky Lambwave (LLW) method is beinginvestigated as a tool for defect detectionand characterization as well as materialproperties determination. Laser inducedplate waves are being studied to developa method of performing rapid couplant-free ultrasonic NDE. Also, IntelligentNDE techniques are being explored(including sensor data fusion) as a meansof in-service corrosion monitoring.

• Multifunctional Automated CrawlingSystem (MACS) - MACS is a

multifunction automated crawlingsystem (MACS) designed and fabricatedto carry miniature instrumentation toperform a wide variety of inspectiontasks while attached to the surface of thestructure of interest. The immediateapplication of MACS is aircraftinspection and various inspectionmodules can be used for this purpose.MACS employs ultrasonic motors formobility and suction cups for surfaceadherence. MACS has two legs for linearmotion and a rotation element forturning, enabling any simultaneouscombination of motion from linear torotation about a central axis. The use ofultrasonic motors, composite materialsconstruction, miniature computer andvideo cameras enables a small, lightweight crawling system with an effectivecarrying capability ratio of about 1:10.MACS I is 11x19 inches and, in itsMACS II new design, MACS II, the sizeis reduced to 10x10 inch.

The target application of the MACS wasthe inspection of the exterior of the C-5aircraft. Currently, there are large areas of theaircraft that are difficult to reach by a personbecause these places are very high up on theaircraft (such as the upper areas of thefuselage and the tail section). MACS will beable to crawl across an aircraft carrying NDEsensors on a pre-programmed path,performing autonomous tests (with the use ofbuilt-in artificial intelligence) and sending data(at present via an umbilical cord, buteventually by radio) back to a computer forstorage and later analysis. These images andsensor data would be sent back to an operatorwho could be at the base of the aircraft, in alocal control room, or potentially anywherein the world. This program is sponsored by


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the Robotics and Automation Center ofExcellence (RACE), Kelly AFB, SanAntonio, TX. The JPL’s NDE & AA Groupleader foresees a potential combination withthe MAUS, which was developed byBoeing/McDonnell-Douglas to performautonomous, multi-mode NDE tasks.

The PC technology can provide a modelfor smart mobile platforms that uses theMACS technology, namely establishing anequivalent to the motherboard. Theavailability of such a platform will offer theNDE industry a basis to develop miniatureplug-in instruments. Robotic inspectioninstrumentation is a multidisciplinary fieldand the ability to specialize in specific areasof the required components will lead toinnovative miniature plug-ins with limitedresources. This can be similar to thedevelopment of such PC products as themodem and many other boards.

The JPL's NDE&AA Group leaderstated that he has a concept jointly with theUniversity of New Mexico for a "snake"robot, so-called boro-robot. Such a robotcan be used to access hidden areas throughsmall openings in aerospace structures toconduct inspection and maintenance tasks.This concept takes advantage of the JPLtelerobotic technology and can beconstructed of multiple elements thatemulates a snake in its dexterity. Eachelement of the boro-robot is made of threeinter-crossed miniature struts and threeindependent linear actuators. The strutssupport and vibrationally stabilize the boro-robot structure and the actuators assure themanipulation capability and dexterity.Without disassembly, a boro-robot wouldenable to inspect and maintain aircraftengines, fuel tanks and other hidden areas of

aircraft structures. As an inspection system,it can be developed to carry CCD for visualtests, fiber optics for transmission of laserpulses to induce ultrasonic test, eddy-current probes for crack detection aroundfasteners and many other sensors.

The J PL NDE&AA Lab is spi nning-offits t echnology to medical diagnosti cs andtreat ment appli cations, u nder NIHspons ored tasks as well a s noninvas ivegeoph ysical pro bing of te rrestrial andplane tary groun d surfaces , under NA SAtasks . The sci entists of this lab are workin gin co operation with vario us univers ities(incl uding UCLA , UTEP and UNM),indus try and NA SA centers to develo p theneces sary techn ologies. Because of theirwork in the are a of actua tors, such asultra sonic moto rs and ele ctroactive polymermuscl es, and ro botics the JPL NDE l ab hasbeen renamed to include a dvanced ac tuatorsin it s title.

5.4.3 NASA Kennedy Space CenterThe instrumentation engineers at the

NASA Kennedy Space Center (KSC) whowork in the Special Development Laboratory(SDL) provide direct technical and operationalR&D support to all NASA Program Offices atNASA Johnson Space Center in Houston,TX. These include the Space Shuttle ProgramOffice and the Space Station Program Office.One component of this R&D support is theNDI/NDE of space qualified components suchas the reusable solid rocket boosters used bythe Space Shuttle.

Regarding NDI/NDE for corrosion, theengineers pointed out that they considersome of their major corrosion problems to bewith components such as the Shuttle SolidRocket Boosters that are re-used after theirrecovery from the salt water environment of


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the ocean. However, this belief is not heldby NASA Headquarters, and thus, fundingfor R&D on NDI/NDE for corrosion is closeto nonexistent.

Despite this lack of funding, the engineersat KSC have developed NDE techniques tosolve recurring problems. SDL engineers, forinstance, are using thermography to inspectfor disbonds in the aluminum honeycombstructure of the rudder speed brake on theshuttle. They consulted with NASA Langleywhen fabricating the system. The technique isalso being used to inspect the Shuttle payloadbay doors. The technique can fully scan onedoor in about a day.

The engineers also are researchingdevelopment of a scanning eddy currentmicroscope. Since funding is limited, they aredesigning and fabricating it from componentspurchased at local hardware stores.

5.5Department of Energy (DOE)

The DOE has sponsored a number ofresearch activities into enhancing NDEtechnologies. Their research is cited in thefollowing paragraphs.

5.5.1 Lawrence Livermore NationalLaboratory

Lawrence Livermore National Laboratory(LLNL) employs 20- 24 people in the area ofNDE, and does about $1M -$2M of workannually in the area. Their goal in the NDEthrust area is to support initiatives thatadvance inspection science and technologyand look to provide cutting-edge technologiesthat show promise for inspection tools threeto five years in the future. LLNL doesresearch in the areas of dual-band infrared,radiography, and ultrasonics. LLNL also doessome work in x-ray computed tomography

and acoustic emissions, and is beginning towork with lasers.

Most of the research conducted at LLNLis in the area of thermography, with a focuson the examination of aging nuclear weapons.For their work, corrosion is not as much anissue as is chemical change. At present,about 50 percent of their work focuses onnuclear weapons, a reduction from previousyears. The Lab also has worked with theFAA on aging aircraft (receiving about$800K over 5 years), the auto industry onmetal matrix composites, the CaliforniaDepartment of Water Resources on dams(receiving about $1M), and the FederalHighway Department, attempting to detectcracks in bridge decks (receiving about$800K over 3-4 years). They have alsoworked with Boeing on composite durabilityfor a high-speed civil transport aircraft (alarge, multi-year effort). Specifically, theyare trying to accelerate the aging ofcomposites, and then test them with NDEtechniques, and to report their findings tothe FAA.

LLNL’s work in radiography is notdirected toward corrosion detection per se,but rather toward new developments inelectronic imaging and image intensifiers.New work is being done in the area ofamorphous silicon arrays for use in lowerdose x-ray imaging using 8” by 8” flat panelimagers (from Xerox) which are notsusceptible to radiation damage. Whilestandard radiography is sensitive down to amaterial loss level of 2 percent, they believetheir electronic imaging techniques will besensitive down to 1 percent. Much work isalso being directed toward computerizedtomography, but they recognize that thistechnique is relatively slow, and hence isbetter used during production than for post-


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production work in the field. They also areworking on x-ray backscatter imaging (i.e.,one-sided x-ray imaging), based on atechnology from Phillips, which produces amap/scanned image by imaging a 2” wideswath which moves at 4” per minute in araster scan pattern. This technique iscurrently used by the Canadian Air Force.

There also is a group at LLNL that hasworked with embedded electro-chemicalsensors to search for corrosion products.

LLNL is pushing toward using datafusion techniques to combine the results ofultrasonic, radiography and computerizedtomography to enhance detection. Since alldata collection is computerized and sent to acentral computer, the possibility of fusingexists and they consider that the payoffsoffered by this data fusion may be great.

LLNL also does all types of traditionalultrasonic work, including C-scans and B-scans, using two large tanks to examine, forexample, lap joints and welds. They haveexperience in the testing/evaluation of a widevariety of materials, including steel,composites and ceramics, and excel in thearea of signal processing (specifically in theuse of neural nets to classify defects andextract information) and high resolutionimaging. They have built a number ofprototype scanners for commercialcustomers, such as the auto manufacturers,and work with vendors to commercializetheir (LLNL’s) designs.

LLNL also has worked with theDepartment of Water Resources (examiningdam tendons, which are 40’ by 1” pipesembedded in concrete within the dams andtheir floodgates). Most of their research inthis area involves laser generation anddetection of ultrasound, including a 4-year,

$1M IRAD program. While this is not assensitive as piezo-electric ultrasound, theyhave worked with Johns Hopkins to domodel-based signal processing schemes toincrease sensitivity. Recently, they haveworked on a DOE project on process controlto listen with an acoustic sensor (specificallyan interferometer beam) to judge the statusof a laser cut being made through a material.The ultrasonics group is more focused on theapplication of technology for DOE thanpure research, especially on the use of fiberoptics to permit laser ultrasonics to beperformed while positioning the lasersoutside of hostile environments.

LLNL uses IR tomography to quantifycorrosion damage, and can detect differencesin thickness of less than 10 percent. LLNLresearchers have pioneered the use of dual-band IR (DBIR) imaging, working in the 3-5and 8-12 micron bands. Flash lamps are usedas the heating source. Their DBIRtomographic (DBIR-CT) technique givesthree-dimensional, NDE, pulsed-IR thermalimages, in which the thermal excitationprovides depth information, while the use oftomographic mapping techniques eliminatesdeep clutter. (In fact, the researchersmentioned that they have worked onalgorithms to distinguish sealant globs fromactual corrosion between the layers of astructure.) The technique createsbackground-corrected thermal maps, and candetect/depict flaws in three dimensions,depicting flaw size and its estimated deptheven in multi-layer structures. DBIR-CTthus permits the detection of low levels ofcorrosion; provides corrosion defect maps inthree dimensions; and results in a lessenedfor exploratory, destructive testing. Thetechnique was developed originally for use inaquifer detection, then was transferred to


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land mine detection, and now has beenapplied to the detection of aircraft defectsand corrosion.

LLNL is moving into the area of thermalinertial maps, which will permit the taggingand removal of foreign material clutter (bothshallow sealants and deep, interiorinsulation) from the images produced by theDBIR techniques. The researchers indicatedthat they can also do crack detection, butadmitted that this work was at a very earlyexperimental stage and the ultrasoundtechniques remain superior. They claim to beable to calibrate metal loss at the five percentlevel with few or no false calls.

5.5.2 Lawrence Berkeley NationalLaboratory

LBNL currently does little work directlyrelated to corrosion detection technologiesper se, but is heavily involved in developingNDE/NDI technologies that could havepotential for detecting corrosion in defensesystems. The Engineering Division doeselectronic instrumentation and detectiontechnology, most of which is nuclear related,and includes x-ray diffraction. TheMechanical Engineering Department designsand builds particle accelerators and theirrelated detectors. Many of the Lab’spersonnel are dual-hatted as professors atCal-Berkeley.

LBNL has been researching NDEacoustic wave technology, particularly laservibrometry, for the auto industry, with afocus on adhesively bonded joints inlightweight materials (such as aluminum).The auto industry has traditionally usedsteel components, welding and destructivetesting, but has been moving to the use ofaluminum/composites, bonding techniques,and NDE. LBNL researchers are exploring

non-contact, fast/real-time, reliable, on-lineNDE techniques and the sensor developmentfor them. They are examining using higherfrequencies (with the drawback of limitedpenetration) to detect smaller defects; inincreasing spatial resolution, requiring moretime per measurement and moremeasurements; and in global excitation.

LBNL began by looking at bonded T-joints in aluminum plates, exciting the plateand using a laser vibrometer to scan thelength of the joint to see if they could getrecognizable, localized resonances at adefect. This technique is fairly sensitive, but,since it requires access to the joint, notentirely satisfactory. They are now lookingat shooting transient waves across the jointand trying to get back projections from anydefects. Their work also includes looking atcomposite plates, using higher frequencies(with their admittedly limited penetration)to cover as much surface area as possible.While this is sensitive to defects, the modeshapes of the returned signals vary with thefrequency of the waves being used,potentially confusing the results. Thescientists are also working on non-contactscanning data acquisition.

In the future, the LBNL personnel hope toexpand this work to consider the test andanalysis of structural members; thedevelopment of excitation sources and sensors;an analytical model; and robotics and controlsystems for the development of scanningheads. This work has been accomplished forthe Office of Transportation Technology overthe past 14 months. It is a small-scale projectin a new field for LBNL.

LBNL has done extensive work in thetesting of energy efficient windows in aclimate lab, using an IR camera for surfacetemperature readings. Their experiment most


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closely related to the area of corrosiondetection involved placing a strip of heaterson one side of a plate connected by a lapjoint to another plate. An IR scanner andsensor is placed on the other side of the jointto detect temperature differences caused bydebonds/defects. This could be applicable tocorrosion detection since corroded areas havea higher thermal resistance than non-corroded areas, but requires access to bothsides of a joint.

5.6Department of Commerce/NIST

To help U.S. industries avoid the negativeimpact of corrosion, NIST and the NationalAssociation of Corrosion Engineers (NACE)joined together to form the NACE-NISTCorrosion Data Program. The objective ofthis program is to use the latest advances ininformation science and technology toprovide industry with convenient and reliableinformation on materials performance andcorrosion control. Working with experts fromindustry, NACE-NIST knowledge engineerswork to develop expert systems, databases,and modeling programs that are distributed toindustry to help avoid corrosion failures. Theoverriding goal of the CDP is to enhance thecost effective practice of corrosionprevention by collecting, organizing,evaluating and disseminating, in computerizedform, corrosion and materials performanceinformation.

Researchers at NIST are also working todevelop improved laboratory and fieldtechniques for measuring and monitoring thechemical reactions that degrade theperformance of materials in service. NIST’sMaterials Performance Group focuses onmechanical properties, deformationprocessing and fracture, and on the effects ofcorrosion on metals performance. The

Group's primary mission is to assist U.S.industry in these areas through thetraditional NIST activities of measurementscience and test methodology, standards,data, and metals characterization. One oftheir current thrusts is on developing reliabledata on materials performance and corrosioncontrol. NIST researchers were instrumentalin the development of transient and staticelectrochemical techniques for assessingcorrosion reactions such as potentiodynamicpolarization, electrochemical noise, acimpedance, and in-situ ellipsometry. Also,NIST researchers have developed methodsfor measuring the corrosion of metals in fieldconditions, such as steel in soil and sea-water, electric utility lines in soil, and ofsteel in concrete. Currently, NISTresearchers are working on in-situ monitoringof electrochemical conditions and using theinformation obtained from electrochemicalmeasurements to predict the performance ofmaterials in service.

5.7Commercially Sponsored Activities

There are a number of ongoing R&Dactivities in the corrosion detectiontechnologies arena, primarily driven by theneed for improved capabilities to detecthidden corrosion in aircraft. Some of themajor activities are documented in thefollowing paragraphs.

5.7.1 ARINCARINC has worked closely with the

Oklahoma City Air Logistics Center oninvestigating technologies that can detectcorrosion in aircraft lap joints and upperwing skins. The work has been conducted inthree phases.

During the first phase, conductedbetween 1991 and 1993, ARINC


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investigated commercial-off-the-shelf(COTS) equipment that could adequatelyscan the lap joints and wing surfaces forcorrosion. The result of the first phase was adetermination that no COTS equipmentexisted to detect corrosion in upper wingskins. COTS eddy current equipment didexist for lap joints.

Phase two of the effort consisted ofinvestigations of emerging technologies todetect corrosion in upper wing skins. Thiswas completed in November 1995. Anumber of promising technologies wereidentified, primary among them ultrasonics.Based upon the phase two results, ARINCis now working on phase three, with goals to1) develop and prototype a single system toscan wing skins and fasteners for corrosion,and 2) optimize COTS products for lap jointcorrosion detection.

5.7.2 Boeing Information, Space andDefense Systems, Phantom Works,Seattle Materials and Processes (M&P)NDE Group

The Boeing Seattle M&P NDE grouphas concentrated on NDE data processing,developing engineering solutions to materialsevaluation, and developing advanced sensors.Their mission is to reduce the costs andtechnical risk of developing and evaluatinghardware by applying advanced physicsprinciples to materials evaluation. Currently,the group is composed of 4 Ph.D. scientists,2 engineers, and 1 technician. Some of thetest capabilities available in-house are anindustrial X-ray computed tomographyfacility, a microfocus X-ray computedtomography facility, full waveformultrasonics, eddy current, portable NDEequipment and a radiation effects laboratory.When bidding contracts, they act as aclearinghouse for the company, integratingthe best technologies into the proposal.

This group uses current s tate-of -t he-artequip ment where possible and develo psnew a pproaches when avail able equip mentprove s inadequa te. Table 5-2 descr ibesBoein g R&D cont racts as o f March, 1 997.


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The Seattle M&P NDE team estimatedthat the microfocus computed tomographyequipment purchased in 1993 has alreadypaid for itself in reduced manpower requiredfor failure analysis and in improved qualityof data. The NDE Data Fusion Workstationis being used extensively on a wide range ofBoeing products because it significantlyreduces the time to develop a new NDE dataapplication, and because it presents theinformation in a highly compressed visualformat that makes it much easier for the

evaluator to comprehend. In regards toachieving higher fidelity, which will lead tofewer false calls, they are working onimprovements to shearography, interactivemultimedia computer based training(IMCBT) and NDE for low observables.The shearography and IMCBT tasks will becompleted in 1998. A prototype handheldinfrared directional reflectometer forevaluating infrared LO surfaces has beenbuilt and tested, and two more are being

Table 5-2. Current Boeing Defense and Space Group R&D Aging AircraftContracts.

Contract Name NDEValue

$K

FundingAgency

Task(s) Description

Novel NDE forCorrosion Detection

$737 WL/MLLP -Atmospheric Neutron Radiography

-Fiber Optic Corrosion Detector

-Neutron Activation

Failure Analysis,Shearography andTraining (FASR)

$676 WL/MLLP -CT for failure analysis

-Shearography improvements to simplify interpretation by enhancing postprocess

image data

-Interactive multimedia computer based training for NDE

NDE Data Fusion $951 WL/MLLP NDE Data Fusion Workstation combiningmulti-mode NDE data to reduce ambiguity

NDE technology forLO airframe structures

$440 WL/MLLP Handheld IR directional reflectometer

Enhanced lasergenerated ultrasound

$603 WL/MLLP Evaluate laser ultrasound system atSacramento ALC

Stripping, repaint ofE-3 radomes

$80 ESC Paint thickness mapping using ultrasonicmicroscope

New E-3 radomes $60 ESC Paint thickness mapping

E767 (JapaneseAWACS)

$40 JASDF Paint thickness mapping

Optical fiber basedNDI system for agingstructures

$200 ARPA Low observable corrosion sensor usinghandheld directional reflectometer


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fabricated for delivery to the Air Force.

Recent examples of applications ofadvanced NDE to Boeing programs includethe following:

• Transferred synthetic apertureprocessing of ultrasonic microscope datato the Operations organization.

• Developed ultrasonic method to measurepaint thickness on AWACS radome(estimated savings of > 8 man years)

• Used CT data to calculate the area ofcomplex parts for production platingoperation (estimated savings of$500K/year)

• Developed precision electricalbonding/grounding meter for commercialaircraft production, which is now in use.

− Measures very low impedances

− 1/6 the weight of previous meter

• Refined eddy current based fiberweight sensor which measures electricalimpedance of carbon fiber prepreg toobtain the aerial density of the fiber.This equipment greatly reduces the costof measuring resin to fiber ratioscompared to solvent extraction methods.

Boeing has completed the evaluation ofthree novel NDE techniques to detectcorrosion on aircraft under contract from theAir Force Research Laboratories (AFRL).These three techniques are; atmosphericneutron radiography, embedded fiberopticcorrosion sensor, and neutron activation.

In atmospheric neutron radiography, theuse of naturally occurring neutrons in the

upper atmosphere was examined as apossible way of imaging corrosion. Aneutron beam which closely approximatesthe atmospheric spectrum was used tosimulate several years of flight exposure, andinsufficient image contrast was found in theexposed image recording materials. Boeingconcluded that the atmospheric neutronradiography technique was not feasible.

The fiber optic corrosion sensor relied onetching of aluminum plated onto a bare fibercore sensor to change the amplitude of theoptical transmission through the sensorregion as the aluminum plating corroded toindicate the presence of corrosion. While thetechnique worked as predicted when a baresensor was subject to corrosion, itsperformance was very erratic and the fiberwas prone to breakage when mounted on apiece of corroding aluminum. Boeingconcluded the technique was too high risk towarrant further development.

The neutron activation techniqueexploits the fact that short half life isotopesare produced when a part is exposed to ashort burst of neutrons. Each isotopeproduces a family of gamma decay photonswhich have characteristic energies as theydecay. These photons can be detected andsorted by energy, allowing assessment of theelemental composition of the part beingevaluated. For this application, Boeing usedthe oxygen in the corrosion products was theelement for detection. In a laboratoryenvironment, aluminum hydroxide equivalentto a thickness of 0.003 inch spread over aone square inch area in the presence ofaluminum metal was reliably detected.Based on these results, Boeing concludedthat this technique warranted furtherdevelopment, which has occurred under


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Boeing internal funding to aimed at detectingshell inclusions in titanium castings.

Under contact from AFRL, Boeing isevaluating the Laser Ultrasound InspectionSystem (LUIS) at McCellan AFB inSacramento. The purpose of this contract isto gain experience with this technology,document lessons learned for future ALCequipment acquisitions, and project futureenhancements to existing equipment. One ofthe key conclusions from this study wasthat laser based ultrasonics (LBU) has amajor advantage over conventionalultrasonics when scanning a part in a regionwhere the outer surface has a sharp radius.On flat or gently curved outer surfaces,conventional ultrasonic techniques in generalachieve better performance as measured bycost, throughput, and data quality. Sinceconventional ultrasonic techniques arerelatively mature and LBU techniques arestill evolving rapidly, these conclusionsshould be considered as a currentassessment, not a final conclusion.

5.7.3 C. W. Pope & Associates Pty. Ltd.C. W. Pope, a commercial NDT and

materials testing company with 115employees, is one of the major navalcontracting NDT companies in Australia,doing substantial NDT for the AustralianNavy in the Newcastle dockyard.

Company representatives highlightedthree specific areas of company expertise:

• Standard pulse echo ultrasonics forfar-side corrosion testing in shipstructures

• Standard pulse echo ultrasonics foruse in the petrochemical industry, toexamine insulated pipelines while thepipe is still on-line

• NDT for aircraft frames andcorrosion in tubing, especially inhelicopters. (Since many of thestructures here are on the order of only 1mm thick, they believe real-time x-raysmay let them look through the tubing toexamine both the internal and externalstructures. They can examine ahelicopter in a single day, taking 25frames).

Radiography and ultrasonics are theirtraditional NDE methods. Real-timeradiography technology is a key area for thecompany, since down-time andenvironmental issues are driving thecommercial power industry in Australia, andthis technology allows the company toprovide improved information to theircustomers in a shorter time, improvingreturn on investment.

Pope also has begun in association withan English firm, AEA Sonomative, that hasdeveloped software to tie a pulse echoultrasonics probe to other software that willproduce graphic images. They are beginningto use B-scan techniques (as a new way topresent data, i.e., in cross-sectional view).This has been used on storage tank floor andpiping inspections. They also are usingmagnetic flux leakage techniques, althoughthey admit that this is less viable inaluminum structures. Finally, they do somethermography, although they have not usedit for fatigue testing or corrosion detection.

The mainstay of Pope’s R&D group isthe use of electro-magnetic acoustic trans-ducer (EMAT) technology for NDE. Thisproduces sound waves in materials using anelectric coil and magnets, sending energyalong a surface to an area(s) to which normalaccess may not be possible. This was first


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used to detect stress corrosion cracking innatural gas pipelines, but company represen-tatives indicated it also can be used to detectcorrosion. However, they pointed out thatthe equipment required is big and bulky, andmust be included in part of the “pig” thatgoes down the tube, performing the inspec-tion. The technology was developed byRockwell in the 1960s for missiles. Itprovides good depth/penetration capabilityand needs no couplant, but sensitivity of thetechnique always has been a problem.

They stated that research people inNDT all over the world are moving towardEMAT, but that Pope is already using it inthe field. Pope has received the largest grantwhich the American Gas Association hasever sent outside the U.S. to explore thistechnology. Others working in this fieldinclude Babcock and Wilcox and NASA.

Characteristics and constraints ofEMAT technology include:

• It is dry, needing no couplant

• It provides a macro inspectiontechnique for large surfaces/areas, and inall but “weird” geometries, microinspections can be performed

• Direct physical contact is notnecessary, so it can be used throughpaint or other surface coverings

• It is not important which side of thesurface the defect is on (i.e., whether thedefect is on the same or opposite side ofthe transducer is irrelevant)

• It has a low false call rate (reliabilityin the “high 90s”)

• It sends out a parallel beam, vice theexpanding beam produced by ultrasonictechniques

• With proper processing, a 3-dimensional wire diagram of the resultscan be produced

• However, size can be difficult toestimate

• The item being inspected must have aminimum internal diameter of a “fewinches” and a “fist-sized” externaldiameter, otherwise resolution is lost.

A real-world example of the use ofEMAT technology is in the inspection ofship fire extinguisher systems. Use ofEMAT techniques could cut the time neededto inspect these systems to a fraction of thehuge amount needed by more traditionalmanual ultrasonic techniques.

Pope generally gets paid by the man-hour and that they essentially have no com-petition in the fields in which they work.Thus, they have no incentive to incorporatenew technologies into their repertoire ifthose technologies reduce the cost whichthey can bill to their customers, especially tothe government.

5.7.4 Diffracto LimitedDiffracto Limited is a small, high-tech

firm that markets D Sight aircraft inspection,(DAIS 250C, DAIS250CV), an enhancedvisual, rapid scan inspection system desig-ned for corrosion detection along lap jointsand surface distortions in the uppermostlayer of the surface. This technology magni-fies surface curvature changes, such aspillowing or bulging between rivets, to theexterior skin of the aircraft, making themreadily apparent. The system is encased intoa movable sensor, which is placed directlyonto the surface of the aircraft.

The D Sight technology is described as adual light pass retro-reflection technique.


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This technology uses a CCD camera, a whitelight source mounted slightly below thecamera lens, and a retro-reflective screen. Asurface targeted for D Sight inspection iseither reflective or made reflective with anenvironmentally friendly highlighting fluid.Light from a source is directed to theinspected surface (primary signal), reflectedto a retro-reflective screen and back to theinspected surface (secondary signal). Theretro-reflective screen, covered withmultifarious silvered glass beads, returns acorrupted pattern of light to the inspectionsurface; not a perfectly mirrored lightpattern

of the primary signal. The resultingsuperimposition of the two light patternscreates the D Sight effect that is captured bya CCD video camera positioned slightlyabove the light source. The image from theretroreflector is seen through the surface nearthe local curvature distortions as bright anddark gray-scale variations. It is the nature,size orientation and contrast of theseintensity variations that determines theextent of the surface deformation andultimately the corrosion level.

A software program has been establishedto both provide a baseline aircraft grid andmap the inspection carried out relative toinspection criteria established in the planningprocess. Large surface areas of aircraft can bemapped quickly with problem areasidentified for more detailed inspection using amore traditional method like eddy current orultrasound. It can also be used to monitorcorrosion growth by comparing previousimages to present images and calculating thedifference. In addition, the system also hascapabilities to determine impact damage andde-bonds on composite surfaces.

Initial research using D Sight as aninspection technology in the aerospaceindustry was funded by the Structures,Materials and Propulsion Laboratory of theInstitute for Aerospace Research (IAR),under the auspices of the National ResearchCouncil Canada (NRCC). D Sight foraerospace continues to be explored byseveral government agencies within Canadaand the US, as well as in Europe.

Diffracto is developing a scanner thatuses Diffracto’s patented D Sighttechnology for the detection of corrosion inlap splices. The goal of this R&D initiativeis to produce enhanced visual D Sight imagesfrom a lightweight, low cost device that can


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be used by one operator and provideslimited data storage capability. The scannerdevelopment phase is scheduled to becompleted by April 1998. The project isPhase IV of a larger program that saw thedevelopment of the DAIS using a full viewapplication of D Sight. This phase of theprogram is being funded jointly by theTransportation Development Centre ofTransport Canada and Diffracto. The TDCfunding level is 70 percent. Earlier phases ofthe program included funding by the DND,FAA, U.S. Air Force and the NRCC, withthe FAA contributing the largest share of thefunding via an international agreement.

The D Sight technology also is used forthe detection of impact damage anddelaminations/ disbonds in composites as wellas any other topological surface anomaly.Other applications include automotiveapplications for the inspection of Class “A”surfaces. For instance, the system is panned tobe used to detect small defects on a premiumvehicle of a large automotive company prior tothe application of paint.

5.7.5 Engineering Testing andResearch Services (ETRS)

ETRS is an applications-orientedAustralian commercial consulting firm.ETRS has a network of 16 offices, making itthe largest single supplier of NDI services inAustralia.

The company is accredited with ISO9001 and has approvals for corrosion surveyof hull structures with DNV, Lloyds, ABSand Bureau Veritas. ETRS also has CASAcertificate approval for NDI as well ashaving approval from commercial aircraftmanufacturers such as Hamilton Standard,Lear jet and many commercial smalloperators.

ETRS is heavily involved in corrosionfailure assessments and suitability ofmaterials for various environments,especially offshore marine structures.Radiography, eddy current and ultrasonicsare being used extensively to assist in themonitoring of corrosion of piping, pressureequipment and marine structure. Ultrasonicsis used with interface triggering for oxidethickness measurements. B-scan ultrasonictechniques are sued for the cross-sectionalpresentation of rear-wall corrosion onstorage tanks and pressure vessels, detectedby standard pulse echo techniques.

The company’s application of corrosiontechniques are used in several areas,including:

• High temperature electro-chemistry,looking at ways to inhibit/reducecorrosion of electrodes caused by theextremely caustic fluids used inaluminum plants

• Electro-chemical power source performance evaluation, assessing how corrosion of battery plates affected performance in telecommunications and military systems

• Sacrificial anode performance in gypsum/bentonite backfill media

• Exfoliation corrosion of high-strength Al-Mg alloys, such as used in high-speedcatamarans and other applications in the shipping industry

• Anti-foulants for aluminum-hulled ships(copper-based formulations)

• Filiform corrosion (in automotive,marine and aerospace applications).


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5.7.6 McDonnell Douglas Corporation(Now a wholly owned susidiary of TheBoeing Company)

The McDonnell Douglas PhantomWorks is very active in NDE R&D and has anumber of laboratories and functional groupsthat support this line of research. Some ofthe NDE methods currently underdevelopment for corrosion detection aremulti-modal, large area scanning, nuclearmagnetic resonance, and computedradiography. From 1992-1997, the companyhas dedicated significant resources tocorrosion detection development, brokendown into the following development stagesand percentage breakouts (see Table 5-3).

McDonnell Douglas currently marketstheir Mobile Automated Scanner (MAUS), aportable C-scan inspection system thatintegrates several traditional inspectionmodes into a single package. Its capabilitiesinclude pulse-echo ultrasonics, ultrasonicresonance, and eddy current. The multi-modal approach allows inspection of avariety of structure types, includingcomposite metallic and bonded assemblies.This system is used in a variety ofmanufacturing and aircraft maintenanceenvironments for quality inspections,damage assessment, repair evaluation, andaging structural evaluation programs. TheMAUS is hand heldand moves along asurface on rubberwheels coupled to anencoder thattranslates positioninformation to c-scanformat. The systemalso has dataformatting andarchiving capabilities.

The e quipment i s portable and easy toset u p, and can quickly i nspect lar gestruc tures. Sca n speeds o f up to 40 0 squarefeet an hour ca n be achie ved.

The MAUS system was developedunder a 1991 USAF contract as part of the“Large Area Composite Inspection System”program. It was developed primarily forscanning large composite structures such asthose found on the B-2 and C-17 aircraft.Using a vacuum-assisted scanning track, theMAUS has been used to scan the DC-10crown skin for cracks. The inspection wasaccomplished in 4 hours, compared with the100 hours required for an equivalentinspection using radiography. This techniquehas been particularly useful for examiningcorrosion in fuselage lap joints, such as thosefound on the KC-135 aircraft.

MAUS development continues under aUSAF ManTech project to further developthe system to incorporate additional bondtesting capabilities and PC-based software.Other goals are to conduct additional fieldevaluations and incorporate change requestsfrom these evaluations, investigate batterypower alternatives, and deliver a fieldhardened prototype.

McDonnell Douglas currently has over30 systems in the field. The USAF has

Table 5-3. McDonnell Douglas Corrosion Detection R&DFunding Profile.

Method Development Stage FundingPercentage (%)

Basic Research 2

Exploratory Development 17

Applications Development 7

Full Scale Development 35

Technology Implementation 39


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MAUS III systems at McClellan AFB,Tinker AFB, Hill AFB, Charleston, Warner-Robins AFB, Kelly AFB, and the Air ForceResearch Laboratory. The Navy hassystems at NAWC Patuxent River and atNADEP Cherry Point. Within industry,systems have been procured by majoraerospace companies in the U.S. On theinternational front, the Royal Air Force(UK) has acquired one system.

McDonnell Douglas is also developingNuclear Magnetic Resonance technology todetermine the presence of incipient corrosionunder coatings. The concept is to pulse thesurface with a tuned RF pulse in thepresence of a magnetic field and measure theresonant frequencies that result. Thistechnique has demonstrated good detectioncapability for corrosion under paints andsealants and moisture detection underthermal tiles on the space shuttle.

Anoth er corrosi on detecti on technol ogyarea that McDon nell Dougl as is purs uing iscompu ted x-ray radiograph y. Basical ly, thistechn ique deals with expo sing a pho sphorcoate d image pl ate to x-r ays and an alyzingthe r eaction of the phosp hors withradia tion. The image plat e reader t hencaptu res the da ta, which is saved i n a digita lfile and transf erred to a data revi ew station for i nterpretat ion on a h igh resolu tionmonit or. This technology is beingevalu ated as a replacemen t for film due toits e xcellent c ontrast se nsitivity. Economic benef its may al so be real ized throu ghelimi nation of film.

5.7.7 PRI Instrumentation, Inc.Physical Research, Inc. (PRI) was

founded in 1980 and is based in Torrance,CA. The company receives about $1Mannually in sales and has had over 200

contracts during its lifetime. The companyhas expertise in electronics (especially highspeed analog to digital converters) and NDE(the company manufactures the Magneto-Optic/Eddy Current Imager (MOI) device,the first one of which was shipped in 1992).PRI is responsible for the R&D aspects ofthe MOI product. Its subsidiary, PRIInstrumentation, Inc., which has the MOI asits sole product, is responsible for productcommercialization.

PRI’s MOI devic e exploits a princip ledisco vered 150 years ago by Faraday whenhe ob served tha t when pla ne polariz ed lightis pa ssed throu gh glass i n a direct ionparal lel to an applied ma gnetic fie ld, theplane of the po larization is rotate d. Thedevic e provides a NDT sys tem forinspe cting ferr ous and no n-ferrouscondu cting mate rials and can detect themagne tic fields associate d with bot h surfaceand s ubsurface defects (b oth cracks andcorro sion). The depth of penetratio n isdepen dent on th e material being tes ted andthe f requency u sed (which can range from1.5 t o 100 KHz) . The lowe r the freq uency,the d eeper the penetratio n for a gi venmater ial, with depths of 0.015” to 0.12”achie vable in 7 075-T73 al uminum. Th eMOI p roduces a direct, an alog image of thedefec t and proj ects that image on a head-mount ed display , while ha ving thecapab ility to s imultaneou sly send d ata to acompu ter for st orage and later anal ysisand/o r to a vid eotape mac hine. The entiresyste m consists of a 6” x 8” x 14” controlunit, a 3-lb. h andset tha t is used to perform the a ctual scan ning of th e surface beingexami ned, and a headset. The system costsunder $30K per unit.

The MOI allows rapid inspection oflarge areas for defects. For example, it was


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stated that the inspection time for a B-52can be reduced from 38 - 40 hours to 3hours. The MOI permits reliable inspectionthrough both paint and decals (reducing, forexample, inspection times for Tower Airfrom 2500 hours to 84 hours), and, since itsdisplayed results are easy to interpret,requires minimal operator training. It hasbeen approved by, among others, Boeing foruse in fatigue crack detection on all modelsof its aircraft; the Air Force on B-52s andKC-135s, with the C-5 in evaluation; and theNavy on C-2s and E-2s.

The latest versions of the MOI rely onsheet current induction, removing therequirement to rotate the unit 90° toeliminate the chance that a crack is parallel tothe eddy current field. PRI claims that earlierversions were about as reliable as standardeddy current devices, while the latest model(with the sheet current induction) is better.Although current models can be used onslightly concave surfaces (as long as lift-offis not excessive), a version (called theRotomag) is in development which will havefeet tailored for pipes, power plant turbineblades, and other curved surfaces. Also indevelopment is a palm-top version (smallerconfiguration) with a CCD camera.

PRI representatives said that the MOIhas a unique capability to detect cracks indimpled countersinks. Its display allows theuser to see the fields which look like thecrack/corroded area. It has the advantage thatminimal signal processing is needed, asopposed to standard eddy current devices,which require heavy use of signal processingtechniques.

Although it originally was used, andprimarily was approved, for crackinspection, the MOI technology is nowrecognized as a useful detection tool for

corrosion. Its use in this area has beenapproved by Gulfstream and is beingevaluated at Tinker AFB and by UnitedAirlines. PRI researchers believe that it could(with processing) generate contour picturesof any corrosion. The scanning movementrequired for use of the unit helps to pinpointcorrosion. It also has proven useful infinding defects in spot welds such as wereused on the KC-135 and the A-10.

5.7.8 Southwest Research InstituteSwRI NDE&T researchers have developed

two technologies they researched specificallyfor corrosion detection: (1) magnetostrictivesensors (MsS), and (2) orthogond axis eddycurrent imaging. Currently the MsS techniqueis used strictly to detect corrosion in steelpipelines. The technology consists ofelectrically inducing an elastic mechanical wavealong the longitudinal axis of a pipe and thendetecting the characteristics of the wave (e.g.,amplitude, wavelength, frequency) both beforeand after the wave travels the length of thepipe. Reflected signals can indicate defectssuch as corrosion in the pipe. A key feature ofthis technology is that it allows inspection oflong lengths of pipe from one access point.Funding for the technique was originallyprovided by the Federal HighwayAdministration and the Gas ResearchInstitute. SwRI is presently looking for othersponsors to continue development of thetechnique.

SwRI has worked with E-Systems toresearch the use of their orthogond axisprobe technique to detect corrosion inaircraft. The orthogonal axis probe providesgreater sensitivity then conventional probesby using transmitter and receiver coils thatare located together but oriented differentlyto avoid electromagetic coupling to eachother. This configuration significantly


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reduces the probe’s sensitivity to liftoffvariations. The research with E-Systemsconsisted of analyzing aluminum skinstructures on Navy P-3 and RC-135 aircraft.No follow-on research occurred with E-Systems.

5.7.9 Thermal Wave Imaging, Inc.TWI is a small business incorporated in

1992 that employs eight people. It isdedicated to the development andcommercialization of infrared thermal waveimaging technology that was initiallydeveloped at Wayne State University. Thecompany licenses Wayne State’s intellectualproperty and has expanded on this patentedtechnology. TWI currently has patentsrelated to thermal wave imaging datainterpretation and the application of heatthrough flash lamps and reflectors to areasurfaces. They have other patents pending.

Thermal wave imaging is a pulsed - 5milliseconds - system that can operate on amidwave 3 to 5 micron infrared band orlongwave 8 to 12 micron infrared band. Thethermal pulses traverse through objects,reflect off subsurface defects, and thenreturn to the surface as thermal wave“echoes.” This technique allows for anaccurate measure of material thicknessdifferences. The spatial resolution isinversely porportional to thickness (ordepth) so the technique works best onshallow defects. The detectors can becomposed of either indium antimonide orplatinum silicide. The IR detector isprepacked and the system is built around thecamera (TWI works with all the majorcamera companies on this.) The system doesnot need to be cooled. The TWIrepresentatives estimated that their systemcan cover approximately one square footevery 15-30 seconds. They consider this

technology as complementary to such pointmeasurement techniques as ultrasound andeddy current by providing non-contact, widearea coverage within a few seconds.

In 1993, TWI introduced EchoTherm - anintegrated system for IR NDE of subsurfacedefects. It analyzes the thermal behavior ofthe sample in response to a controlled heatpulse and is touted as being easilyinterpretable, highly repeatable and immuneto variations in ambient conditions. Thesystem consists of a pulsed heat source(typically, high-power photographic flashlamps), an IR video camera, and imageprocessing hardware and software controlledby a personal computer. It is fully digital andincludes PCI-based image acquisitionhardware; a Windows based softwareprogram for data analysis; flash lamps andoptics for maximum uniformity, minimumafterglow and short duration; a programmableflash power supply; and a portable Pentiumcomputer. EchoTherm is configured for eitherlaboratory or field use and is compatible withall leading IR focal plane array cameras.

TWI representatives cited that thebenefits of the TWI technology include itsability to scan a wide area quickly andprovide fast, quantitatively defined feedbackwith minimal operator interpretation. Theystated that it is easier to interpret thantechniques based on optical interferencemethods. Thermal wave imaging measuresthe time at which things occurred and not theamplitude as opposed to conventionalthermography where only the surfacetemperature of the part is measured. It canbe employed on aluminum, plastics, steel,and composites like graphite epoxy. It is lesseffective when dealing with highly insulatingmaterials like rubber or glass.


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There are, however, a few limitations.Images created by defects deep below thesurface tend to blur. When testing highlyreflective metals, operators will have to coatsurfaces with water-soluble solutions to helpabsorb the IR light and provide betteremissivity for the cameras.

The cost of the TWI system is $110Kper system - $60K for the camera and $50Kfor the other components. The TWI systemuses COTS products whenever possible andthey have built the system with openarchitectures so that if one module changes,the whole system does not need to bescrapped.

TWI has R&D contracts/testing with orsystems in place at the Navy, NASA,Boeing, Lockheed Martin, HarvardUniversity, GM and Ford. Several TWIcustomers, including Boeing, LockheedMartin, and General Electric, have boughtmultiple systems.

TWI has two SBIRs with the Navythrough the NAWC. One involves reducingthe current TWI system to a handheld unitby minimizing the power requirements forthe shipboard system. The other entailsdeveloping an integrated ultrasound IRsystem using an ultrasound or eddy currentprobe on the IR picture for use in definingdepth measurements and material loss incomposites. TWI’s NASA work deals withassessing composite material delamination/impact damage. Boeing employs four TWIsystems for commercial applications, mainlydealing with detecting adhesive bonding andcorrosion in metals and composites. Fordand GM use these systems for testing in theproduction process.

The TWI representatives foresee thebiggest market for their technology in the

commercial and military aircraft industry.Other applications the company hopes willdevelop into a big market is automatedinspection facilities and petrochemicalpipeline inspection.

As to potential new customers, TWIbelieves that many of the largest compositemanufactuers are looking to replace half oftheir imaging ultrasound systems with newtechnology.

5.7.10 Tektrend InternationalTektrend is a Canadian commercial

company that designs and manufacturescustom NDE equipment for government andcommercial clients. It is a small company,employing 25 people, of which 20 areengineers, scientists, and technicians.

Tektrend’s business is divided betweenmanufacturing and R&D. Manufacturingcomprises 70 percent of the business, R&D30 percent. Saleswise, 90 percent ofTektrend’s sales are to U.S. commercial andgovernment entities; 10 to 15 percent of salesare to the U.S. and Canadian military. Mostof Tektrend’s manufacturing and R&D, 75-80percent, is focused on ultrasonic products.The remaining 20 percent-25 percent iscomprised of manufacturing and R&D ofacoustic emission, eddy current, andradiography products.

Tektrend sells a wide range of products.They sell a hand-held 2-axis ultrasonic testerthat costs $48K. They also sell 6-axisdesktop and 9-axis floor model ultrasonictesters that range in price from $50K to$250K. The costs of these systems includetraining and software installation. One otherimportant ultrasonic product developed byTektrend is an automated pressure hullintelligent ultrasonic inspection system forsubmarines in drydock. Equipment is custom


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built to fit the client’s needs and includeindustrial manufacturing systems.

One R&D area that the company isconcentrating on is electromagnetic acoustictransducers (EMATs). Their researchersbelieve that recent developments byTektrend and others in this area couldrevolutionize ultrasonics. Up until thepresent, EMATs have been very costly.Tektrend and others are bringing down costby reducing the size and using atate-of-the-art magnet and electronics.

5.7.11 TPL, Inc.TPL is a small business headquartered in

Albuquerque, New Mexico whose areas ofproduct development include electromagneticsensors, electrical impedance spectrometers,(EIS), and real-time digital x-radiographysystems.

Their EIS product line, dubbed“Dielectroscope” is used for characterizationof heat damage in composites, for evaluationof protective coatings such as paint on shiphulls and for detection and characterization ofmoisture in composites.

They have developed a suite ofmagnetometer-based NDE sensors, calledAdvanced Penetrating ElectromagneticTechnology (APET), which have muchimproved low-frequency response comparedwith conventional coil-based eddy currentsystems. These sensors are used to detect andimage deeply buried cracks and corrosion inconductive materials.

TPL’s real-time, digital x-radioscopyprogram is based on a high frame-rate, largearea (8.5”x11”), radiation hard imaging array.The system offers high spatial resolution and adynamic range (depth) exceeding that of film.As a result, there is no need to “bracket” anexposure range. The system is currently beingapplied to NDE, tomography-basedcoordinate measurement and medicalapplications.

5.7.12 Utex Scientific InstrumentsUtex is a Canadian commercial company

that designs and manufactures custom highresolution ultrasonic NDE equipment, anddevelops “NDE Workstation” software tocombine and display results from amultitude of NDE technologies, eitherseparately or simultaneously. It is a smallcompany, employing 10 people.

Utex incorporated in 1991 and has R&Dand marketing departments. Approximately60 percent of Utex’s revenues are spent onR&D related activities. All manufacturing ofthe ultrasonic instruments is outsourced.70-80 percent of Utex’s sales are exports toeither the U.S. or European countries. Utexhas no current funding from DND or theU.S. DoD.

Utex makes two different UltrasonicPulser Receivers, the UT320 and theUT340. The receivers are designed to be highresolution in both power and frequency.Table 5-4 indicates some of the current usersof Utex’s pulser receivers. Most of the usersof Utex products also employ the Utex“Winspect” software.


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Winspect has become the de factostandard “NDE Workstation” software,currently holding 50 percent of the market.The software is completely independent ofthe type of NDE technique used. Utex wasthe first NDE software vendor to convertentirely to the Windows operating system.

Utex has been selling Winspect since1995. When first released, it was targetedprimarily at the research market to gauge

what needed to be improved. Since then,they have marketed Winspect heavily toaircraft OEMs. They are currently workingwith Lockheed Martin, McDonnell Douglas,Northrop Grumman, and Boeing. In fact,Winspect has been designed to interface withthe McDonnell Douglas MAUS NDEdevice. Utex has also begun marketingWinspect to the pipeline industry.

Utex is currently developing NDEdatabases to store historical NDE data. Utexbelieves that Winspect is several years awayfrom being a true data fusion engine, which isone of the ultimate goals for the software.

Utex has also developed Imagine3Dultrasonic simulation software, which is alsobecoming an industry standard.

5.8Commercial Airline Activities

The following paragraphs highlight someof the ongoing commercial airline activities inregards to corrosion detection andmaintenance. These writeups are intended asa representative sample of the industry, not

all inclusive. Since 1975,corrosion has been acontributing factor in atleast 687 commercialaircraft accidents/incidents,resulting in the loss of 87aircraft and 81 lives.

5.8.1 Aloha AirlinesAloha Airlines

representatives stated thatthey follow the proceduresof Boeing’s CorrosionPrevention and ControlProgram, which is outlinedin Airworthiness Directive90-25-01. The basic

elements of the program are inspection ofprimary structures; initial and repeatinspection intervals based on calendar timerather than flight hours; maintenance such ascleaning, inspection, rework, and corrosionprevention treatments; and periodicadjustments to the program in order tomaintain a corrosion severity of Level I.Aloha Airlines inspectors are trained at andlargely depend upon visual inspection astheir primary mode for inspecting forcorrosion.

5.8.2 Air Canada - DorvalAir Canada is the largest Canadian

airline. The Dorval Airport location in

Table 5-4. Some Users of Utex Pulser Receivers.AECL Chalk River Labs NASA Lewis Research Center

College of William and Mary National Research CouncilCanada

Electricite de France Ontario Hydro

Electricity Corporation ofNew Zealand

Pacific Gas and Electric

Imperial College of Science,Technology and Medicine

Pratt & Whitney Canada

Iowa State University Southwest Research Institute

Los Alamos NationalLaboratory

Wright Patterson AFB


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Montreal is the site of a large Air Canadamaintenance facility. Like all Canadianairlines, Air Canada is regulated byTransport Canada, the Canadian equivalentof the U.S. Federal Aviation Administration(FAA). The use of NDT techniques in theperformance of routine maintenance on AirCanada’s passenger aircraft is one of theareas regulated by Transport Canada. Forthe most part, visual techniques are theprimary techniques required by TransportCanada. Therefore, those are the techniquesmost widely utilized by Air Canada. Theyhave the capability to do eddy current andultrasonic inspections, but not on a largescale. The Air Canada engineers felt that theeconomics of airline maintenance does notjustify the use of other NDT techniques.They also stated, though, that they do notbreak out corrosion costs separately socould not quantify what corrosionmaintenance is currently costing.

5.8.3 Northwest Airlines, Minneapolis,Minnesota

Northwest Airlines primarily relies onvisual inspection when conducting inspectionsfor corrosion detection. They have, however,been very active in testing new/enhancedcorrosion detection technologies and viewthermography as a technology that shows realpromise and could offer potential large savingsto the airline.

Northwest Airlines NDE professionalsasserted that the airline problem is driven byboth the physics of corrosion and thedirectives of the FAA. For example, thecorrosion AD requires that any corrosiondetected during visual inspection be repairedbefore returning the aircraft to service. Itdoes not specify an allowable degree ofmaterial loss or involvement. NDEinspection of fuselage lap splice repairs

establishes a 10 percent material lossthreshold for repair. Thus, on one hand, anairline may not want to know aboutcorrosion losses of less than 10 percentbecause that leads to unnecessary repairs.On the other hand, it has to know when 10percent has been exceeded. This logicallyleads to an accuracy requirement in sensingtechnology on the order of 1 or 2 percent.

The airlines use structural repair manuallimits to establish three levels of corrosion.Level One is within SRM limits and can berepaired using cleanup methods. Level Twois a higher degree of material loss thatrequires repair or replacement of theoffending parts. Level Three is a seriousmaterial loss that affects the structuralintegrity, and therefore the safety, of theaircraft. It is at Level Three that notificationof the OEM and the FAA would berequired. The airlines distinguish betweenprimary and secondary structures in dealingwith corrosion repair. For example, the areasaround lavatories and in bilges are routinelyexamined and treated as normal maintenance.The involvement of spars, attach fittings andlanding gear would be much more serious.

The experience at NW highlights thecomplexity of the corrosion problem. Inmany cases, repair of corrosion seems toincrease the rate at which it returns andgrows, suggesting that the cure can be worsethan the disease. A significant needexpressed was that of understanding andtracking the rate of corrosion growth toestablish better inspection and repairintervals. There was consensus thatcorrosion removal generates someunknowns, particularly regarding fatigue lifeand future tendency to corrode in therepaired area. They stated that the scientificunderstanding of corrosion is not as


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complete, nor is corrosion as well modeled,as is crack growth and fracture mechanics.The interactions between fatigue andcorrosion are not well understood. Thisinteraction is exhibited in stress corrosionparticularly.

The airline maintenance is treatedprimarily in economic terms within theoverall safety guidelines. As it happens,aircraft are retired for several differentreasons. In some cases, retirement is drivenby the engines and in others, by the airframe.New aircraft are delivered with a designlifetime. This lifetime is often doubled ortripled as various modifications andimprovements are made. It is not unusual fora fleet aircraft to be in its second or thirdlifetime (based on the original design). Thusit is essential to track and understand themaintenance and overhaul history of everyaircraft on an individual basis. The airlinerepresentatives stated that the airlines freelyshare this sort of maintenance informationwith each other.

Northwest representatives noted thatthey must justify investment in costlycorrosion detection tools, as anyunscheduled or unplanned maintenance has adirect impact on operations. They pointedout that airlines must adhere to safetyguidlines but should also avoid flight delaysand cancellations.

5.8.4 Qantas AirwaysVisual techniques are still the major

corrosion/defect detection means employedby Qantas. Qantas representatives statedthat they believe it is “hard to beat” humaninspectors. They did note that too littleconsideration is given to in-service corrosionissues during the design stages of an airtransport’s life. The 10 percent ‘threshold’

is employed only if the OEM reducespermissible tolerances: the representativespointed out that they “see no use” for itunless degradations of greater than 10percent are legitimate problems. Qantasworks under Australia’s Civil AviationSafety Authority (CASA) certificationprogram, which follows Boeing’s CorrosionPrevention and Control Program (CPCP).Qantas has a good relationship with Boeing,so they feel they can suggest changes in theircorrosion detection procedures as necessary.

Corrosion inspections are normally donewhen the aircraft undergoes a check visit.Thus, corrosion control is tied tochronological time vice flight hours oroperational use. In general, the entire aircraftis not inspected. Rather, attention is focusedon known trouble points. In essence, theylook for corrosion where the OEM tellsthem to inspect. Qantas personnel statedthat even tap tests are sufficient in certainareas where they are known to be adequate,and that anyone can do such a test at anytime without needing specialized equipmentor trained personnel. If corrosion is detected,it is dealt with immediately. However, if thecorrosion is found at the end of theinspection and is not deemed so bad as to bea safety concern, elimination of the corrosionmight be delayed until the next inspection.They stated that corrosion is at least “madesafe” when it is found.

Qantas personnel expressed satisfactionwith the process used at Qantas, feeling thatall detected corrosion is removed and thatQantas’s corrosion prevention program isworking well. However the representativesfeel intergranular corrosion is not welldetected by non-visual NDT technologies,leaving much of the detection effort to theeyeballs of their engineers who do visual


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inspections. They did say that second layercorrosion is a problem, since they are limitedin what they can see/detect and what theycan do about it once detected. The Qantasrepresentatives believe far side corrosion canbe resolved, but that second layer is moredifficult.

There was some debate about whethercorrosion returns faster once it has beenrepaired. One representative asserted that itdepends on the nature of the repairs: shoddyrepairs do cause more problems than theyeliminate, but corroded areas which aretreated and sealed correctly will not causesubsequent problems. The need forcorrosion prevention also was emphasized.

Qantas representatives stressed thattheir NDI branch is not an R&Dorganization. While the airline may havesome facilities, they have neither theinclination nor the mandate to performR&D-type operations due to the costinvolved. The OEMs also have a say in theR&D process, either accepting or rejectingnew NDT schemes.

The return on investment (ROI) of theNDI group is important, and the period overwhich they must show a return is shrinking,being about 12 months now. Thus, while thestaff can see the benefit of scanning systems,they cannot justify their purchase at thistime. The NDI group representatives alsostated that maintenance organizations arealways asked to minimize expenditures:from the point of view of management,spending money to put video screens inevery seatback may be more desirable thanspending it to improve maintenanceequipment.

Qantas representatives stated thatAnsett Airlines (a domestic competitor) uses

Airbus aircraft which have experienced agreat deal of water-caused delamination ofthe composite materials used in the aircraft.Thermography was used to detect theseproblems. Ansett monitors the problem, butdoes not fix it unless necessary.

The airline’s use of radiography has beenlimited by a number of factors. The primaryone is environmental issues. Radiography isnot very ‘green’, due to the radiation itself,the heavy metals on the film and the noxioussolvents required. However, the staffadmitted that radiographic film and imagesare the standard against which all otherimaging systems are compared and thatpeople like to see a hard copy of results.

They feel that the sensors used inthermographic systems are getting betternow and Qantas is considering acquiring aninfrared capability within the next year.

As an aside, Qantas representativesstated that the CASA (Australia’s equivalentto the FAA) has lost its NDT capabilitycompletely, as its remaining engineers havelittle or no expertise in NDT. Even accidentinvestigations are performed commercially inAustralia.

The representatives feel that corrosiondetection should consist of three parts: abroad scan, a supplementary analysis toquantify the extent of a problem, and anengineering approach to marry the corrosiondetection effort into the aircraft’smaintenance plan. They believe compositesmay be over-inspected just because of theunfamiliarity of the airlines with thatmaterial.

Qantas used to keep its planes for 20,000flight hours and then sold them. Now, someof the airframes in their fleet haveaccumulated over three times that amount of


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flight time. While Qantas flies in a relativelybenign environment (long flights without a lotof frequent landings and takeoffs), theextended use of their aircraft into whatpreviously would have been considered to betheir third or later design lives has heightenedtheir awareness to and concern with the effectof corrosion on those structures.

5.9University/Academic ResearchActivities

5.9.1 Carnegie Mellon ResearchInstitute

The FAA has funded this institute todevelop an aircraft inspection robot calledthe Automated Nondestructive Inspector(ANDI). This robot, when completed, willbe able to walk over, under and aroundaircraft fuselage attached by suction cups onits seven feet. It will be able to carry outoptical inspections as well as eddy currentand ultrasonic inspections. A prototype wastested at USAir’s maintenance facilities.

5.9.2 College of William and Mary,Department of Applied Science

The Department of Applied Science(AS) at the College of William and Mary hasa number of ongoing NDE Ph.D. researchprojects, including:

• Lamb Wave Tomography

Research Partner: Physical Sciences, Inc.(funded in part by ONR)

• Photo and Thermo-elastic NDE

Research Partner: Stress Photonics, Inc.

• Thermographic Penetrant NDT

Research Partner: NAWC/AD

• Laser Ultrasonic NDE

Research Partner: NASA NESB

• Thermography and IR Microscopy

Research Partner: Stress Photonics, Inc.

• Large Ultrasonic Phased Arrays

Research Partner: NASA NESB.

In addition, the Department of AS isresearching numerical and analyticalmodeling techniques for all NDE methods,and is investigating using neural networks,fuzzy logic, and expert systems to processNDE test data.

The College of William and Mary staffbelieve the ultrasonic lamb wave techniquecan have applicability for detecting corrosiondamage though they consider this techniqueto be at least one year away fromcommercialization.

5.9.3 Iowa Sate University, Center forNondestructive Evaluation

As mention earlier, the FAA has set upthe Center for Aviation System Reliability(CASR) at Iowa State University to overseeinspection system development. Theirresearch programs are described in the FAAsection.

Iowa State University also is the parentorganization for the Institute for PhysicalResearch and Technology, under whichresides the Center for NDE. The researchersat the institute are generally not full timeprofessors but, rather, full time researchers.The technical staff is both full time and somepart time students from the university. Theinstitute has existed since 1984, hasapproximately 100 total staff, and has anannual budget of approximately $8M peryear. There are 22 sponsoring organizations,including the National Science Foundation,the FAA and NIST.


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One of their main areas of research is inthe eddy current technology. Their research isfocused on the control of the probe through acomputer controlled scanning system and theprocessing of the data to generate C-scan(color “3-D”) images of the structure beingexamined. With this approach, the researchersare able to analyze material loss on the backside of the top layer, the top side of thebottom layer, and the bottom side of thebottom layer, subject to the usual limitationsof an eddy current system. They are notworking specifically on multiple frequencyscanning at this point. The goals of thesystem they are developing are that thesystem be inexpensive, portable, light weight,and provide quantitative results. Theirprototype system, using a ruggedized 486portable computer, displays corrosion lossboth by surface and by depth. Testspecimens run from 0 to 30 percent materialloss with an accuracy within a few percent.

The Iowa State researchers are alsoworking on a low energy, energy dispersiveapproach to X-ray radiography. Again, theirfocus is on the computer processing of thereal-time data. Their approach is analogousto color photography as opposed to B&W.The researchers foresee this technology asleading to both the characterization ofcorrosion and, perhaps more importantly,the validation of other techniques that wouldbe more efficient and less expensive. Becausethey are dealing with low energy X-rays,they perceive the shielding problem as minorcompared to current industry standardsystems.

Another technology they are developingis the Dripless Bubbler system designed toemploy ultrasonic sensors in areas andlocations that are otherwise very awkwardor impossible due to the need to employ a

coupling fluid between the probe and thesurface to be inspected. This devicesurrounds the probe with water containedby concentric brushes (rings of bristles).Water is pumped into the cavity by apneumatic pump and removed by a vacuumsystem. Thus, this device can operate onvertical and curved surfaces and works bestinverted as on the underside of wings. Thissystem is able to display C-scan and B-scanside-by-side as a means to distinguishbetween de-bond and corrosion. The focusof this research is the manipulation of theprobe and the associated data processing .The payoff will be more rapid surveys ofcomplex areas subject to the limitations ofthe sensing technology.

Iowa State also houses the newly formedAging Aircraft Center of Excellence (AACE),an FAA sponsored industry/ academiaconsortium that is now focused on advancedmaterials, landing gear, and crash worthiness.It is an outgrowth from the previouslymentioned Center for Aviation SystemReliability, also at Iowa State. The AACEhas corresponding responsibilities to theAANC and the Engine Titanium Consortium(ETC), also sponsored by the FAA. Becausethis center is new, no specific results can becited as of yet. The AACE is emblematic ofthe concentration of FAA sponsoredresearch activities at Iowa State University.

5.9.4 Johns Hopkins LaboratoryThe Johns Hopkins Center for

Nondestructive Evaluation was establishedin 1984 as an interdivisional, cross-disciplinary program of research andinstruction in nondestructive evaluation andmeasurement science and technology.


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5.9.5 Royal Military CollegeThe Royal Military College (RMC) in

Kingston, Canada performs scientific andtechnical research to support CanadianForces. RMC collaborates with all researchorganizations within DND and providesresearch opportunities for scientific andtechnical personnel.

RMC has instituted a Unified CorrosionControl and Preventative MaintenanceProgram. The program has three majorcomponents:

• Predictive Modeling

• On-board monitoring

• Rationalization.

The rationalization thrust is comprisedof an Information Processing subcomponentand includes the development of a designtool RMC calls MSG-3.

RMC personnel are focusing on on-board monitoring and information proces-sing projects. In the area of on-board moni-toring, RMC has two ongoing researchprojects: (1) Aircraft Corrosion Surveillance,and (2) Development of On-BoardCorrosion Sensors. In the latter project,RMC is working with Patuxent River NavalAir Warfare Center and Australian research-ers via a TTCP researching imbedded elec-trochemical sensors. As part of the thrustarea, though, RMC is also researching thefollowing types of potential on-boardcorrosion sensors:

• Electrical resistance

• Linear polarization resistance

• Zero resistance ammetry

• Potentiodynamic polarization

• Electrochemical impedance spectroscopy

• Electrochemical noise.

In the information processing area, RMCpersonnel are working on a project entitled“Knowledge Based System for MonitoringCorrosion in Aircraft.” In this effort, RMC isdesigning an information architecture that willinclude historical maintenance databases thatthey hope will ultimately be capable of fusingand displaying inspection results fromnumerous NDT techniques simultaneously.

The RMC neutron radiography facilityhas been used on a collaborative effort withQETE to inspect the composite controlsurfaces of CF-18s. Currently, it takes sevento eight days to inspect one-half of thesurfaces on a CF-18 using neutronradiography. RMC’s goal is to optimize thesystem and drop the inspection time in half.

5.9.6 UCLAUCLA researchers are studying the

characteristics of materials degradation dueto corrosion and fatigue in aerospace andaircraft structures, specifically aluminumalloys and advanced composites. Theresearch is supported by the AFOSR andONR. They have examined crack initiation inaluminum plates with multiple holes andpits in order to be able to quantify the degreeof corrosion in a structure.

The UCLA researchers focus is onultrasonics. They have developed a guidedwave based technique to determine thepresence of hidden flaws in aluminum lapsplice joints, and the stiffness degradation ofcomposites subject to fatigue loading.

UCLA is currently developing a techni-que to detect the presence of very smallcrack-like defects in structural components


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using an active method involving the initia-tion of cracks. In addition, the UCLA re-searchers are examining laser shock peeningto prevent corrosion, using a layer to shockthe surface of an object to improve its corro-sion resistance. This work is still in thepreliminary R&D stage. UCLA will test theshocked samples for fatigue.

5.9.7 University of Dayton ResearchInstitute

The Univ ersit y of Dayto n Res earch Ins titut e (UD RI) i s cur rentl y con ducti ng apro gram entit led “ Autom ated Corro sionDet ectio n Pro cess/ Syste m for Cos t-Eff ectiv e Mai ntain abili ty.” Thepro gram is is sued throu gh Wa rner Robin sAFB , and moni tored by t he ND E Bra nchof the A ir Fo rce R esear ch La borat ory a tWri ght-P atter son A FB. T he pu rpose ofthe prog ram i s to devel op an d app ly ne wcor rosio n det ectio n tec hnolo gies andcou ple t hese with autom ation tech nolog yto provi de si gnifi cant maint ainab ility imp rovem ent o f the C/KC -135 or si milar typ e air craft thro ugh:

• Accurate corrosion detection at lessthan ten-percent thickness loss

• Reduced person-hours to effectcorrosion inspections throughautomation

• Reduced aircraft flow time

• Efficient discrimination through datafusion techniques

• Accurate reproducibility ofinspections from aircraft to aircraftthrough inspection systemreproducibility.

There are several tasks on this program.UDRI is developing a formalized approach to

corrosion detection technology assessment.This includes definitions of corrosion metrics,specimen designs, NDE output, and analysismethodologies. Several different specimendesigns are being considered. Specimens willbe both real aircraft lap joints and doublersections and engineered panels with variousconfigurations and profiles of thickness lossand corrosion by-products.

UDRI is also optimizing via subcontractseveral NDE technologies includingthermography, radiography, ultrasonic andeddy current inspection methods. Afteroptimization, each technology will beevaluated according to the technologyassessment methodology described above.Corrosion detection technologies eitherdeveloped or advanced by NASA LangleyResearch Center will also be investigated.

An analysis is being conducted in parallelwith this effort in which various automationconcepts are being studied for inclusion inthe program. The analysis is based uponinputs from several vendors, and examinesthe feasibility of the various automationconcepts including implementation, cost andrisk issues. After this evaluation andanalysis phase, one or more NDEtechnologies will be selected for inclusion inthe integration phase of the program, inwhich the NDE system will be integratedwith a selected automation concept and acentral controller. The


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resultant prototype will then bedemonstrated in an inspection of aircraftstructures on a KC-135 tail section.

UDRI is also identifying the datanecessary to provide clear, accurate andcomplete corrosion inspection results. Ifmore than one NDE technology is chosen forintegration into the system, then a datafusion environment will be required toefficiently provide the necessary informationto the maintainer. UDRI is developing thisdata fusion environment and willdemonstrate the results as part of thesystem demonstration described above.

UDRI will also be developing proceduresfor quantifying the reproducibility ofinspection results and certifying inspectionreliability results. These procedures willthen be used to characterize the corrosioninspection system being developed on thisprogram.

UDRI has also conducted an NDErequirements survey addressing differenttypes of damage and structural and mainte-nance characteristics. This study has sur-veyed USAF System Program Managers andother government and aerospace individualsand organizations. The results will besummarized in a report to the government.

5.9.8 University of PennsylvaniaThe focus of the UPenn program has been

on defining the corrosion fatigue mechanism onaircraft aluminum alloys. The ethos of theprogram is that corrosion and fatigue are notseparable but part of the same mechanism.Both aircraft manufacture and aircraft designcontribute to whether the craft is susceptibleto stress corrosion/corrosion fatigue or not.The University has embarked on a program todevelop an electrochemical fatigue sensor forthe U.S. Air Force.

5.9.9 University of WashingtonThe Applied Physics Laboratory is a

research unit of the College of Ocean andFishery Sciences at the University ofWashington. It employs approximately 250science/engineering professionals andsupport staff in six departments.

The Ocean Engineering Department isthe main department dealing with the issueof corrosion, primarily in the area of marinecorrosion. They have done a lot of workinvolving shipboard sonars and are currentlyworking on corrosion resistance testing ofunderwater fiber optic cables, CHT tankinspection, and wall corrosion detection. TheUW group provides corrosion monitoringinstrumentation that can be used on tanks,vessels, and pipelines.

The department’s main source of fundingis the Navy through a NAVSEA omnibuscontract. Their main sponsor is ONR,largely through their Ocean SciencesDirectorate. Total program size isapproximately $25M.

5.9.10 Wayne State UniversityDr. Robert Thomas, along with Dr.

Lawrence Favro, two professors of WayneState University, invented and patented thethermal wave imaging technology. Thisthermal wave imaging technology is a handheld inspection technique that quantifiesinformation on corrosion and operates usinga focal plane array camera with a 3 to 5micron band infrared wave band. Thetechnology is considered especially effectivewhen dealing with a single skin or workingon wing fasteners. The system measuresmaterial loss and lap-splice corrosion as wellas indicating de-bonds in compositematerials. Thermal wave imaging can domultiple layers if there is a sealant between


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layers but is best when used on the firstlayer. It is a lot more trouble to work withwhen inspecting lap splices.

The camera of the Wayne State systemweighs seven to ten pounds and it isestimated that inspectors could inspect theentire belly of an aircraft in one day. The realtime-consuming aspect to the technology isin the recharging of the flash lamps. TheUniversity is working on improving thisaspect.

Wayne State has received funding fromthe FAA Airworthiness Assurance Center atSandia and the Air Force Office of ScientificResearch. The university’s ongoing researchinvolves examining improvements incameras, power supplies, and softwarealgorithms.

5.10 Summary

There are a number of different researchand development activities ongoing in thefield of corrosion detection technologies. Amajor thrust of the research being conductedis for detecting hidden corrosion in aircraft.The defense departments are the leaders inpursuing technology developments, drivenby their need to extend the service life oftheir current defense systems while reducingmaintenance costs due to the decline indefense budgets. Much of the funding foracademic research in this area is provided bythe defense departments.

6. Corrosion DetectionTechnologies IndustryDemographics

Although a few simple industrialapplications of nondestructive testing (NDT)began to emerge decades before World War II(primarily x-radiography), most of the

modern techniques (e.g., ultrasonics,fluorescent liquid penetrant, eddy current,computed tomography, etc.) have beeninvented/developed since the 1940s and1950s. Application of nondestructiveinspection (NDI) processes to aerospacematerials, structures and vehicle systemsbegan to accelerate in the 1960s and 1970swith the emergence of new aircraft structuresdesign philosophies (both commercial andmilitary) to control fatigue cracking, includingearly nondestructive crack detection. Thestate-of-the-art advances that have evolvedover the last 25 years (particularly the lastfive to ten years) have provided a strong basefor many important inspection processes thatare helping to support safe and reliable fleetoperations.

Corrosion detection is one small nichemarket of the NDE/NDT industry.NDE/NDT equipment suppliers and serviceproviders are not dependent upon thecorrosion detection market for theirlivelihood. In fact, the NDE/NDT end userindustries run the gamut, including defenseaerospace, commercial aerospace,automotive, shipbuilding, chemical/petrochemical, construction infrastructure,electronics/electrical, energy (utilities),ordnance, and railroad. The followingsubsections highlight the major equipmentsuppliers and the industry outlook for eachof these technology areas.

6.1Visual

Vis ual i nspec tion is th e ins pecti onmet hod m ost w idely used to i nspec t for cor rosio n. Ma inten ance inspe ctors pre domin antly rely on v isual insp ectio ns -app roxim ately 80-9 0 per cent of th e tim e -to uncov er co rrosi on pr oblem s. Th oughthi s typ icall y ent ails an in spect or wi th a


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fla shlig ht, t here are m any a dvanc ed op tical pie ces o f equ ipmen t to condu ct a moresop histi cated insp ectio n, in cludi ng fl exibl efib ersco pes a nd ri gid b oresc opes, vide opro bes, inspe ction craw lers and r obots ,fib er op tic s ensor s, an d las ershe arogr aphy.

There are over 50 companies that offerthis type of equipment to the NorthAmerican market, a market valued at over$200M.

6.1.1 Equipment ProvidersFiberscopes and borescopes are the

largest product sector in this technology areaand are used in the inspection of engines andairframes. They are considered a subsectorof the medical endoscope market, a marketthat is expanding due to the increased use ofnon-invasive techniques in medicine.Because of this, the advances made in themedical arena profit the industrial market.

Flexible fiberscopes use a bundle ofoptical fibers to show an image from aninspection area to the user’s eye or to acamera. This type of equipment contains aneyepiece, an insertion tube, a bendingsection, and a distal tip. They range in pricefrom $2K to $10K, depending on the degreeof sophistication and manipulation required.

Rigid borescopes work in much the sameway as flexible fiberscopes in that they bothrely on a fiber-optic bundle to illuminateremote spaces. What distinguishes the two isthat borescopes convey an image by a seriesof lenses in a rigid tube vice a bundle ofoptical fibers. And, borescopes require astraight line of access.

Many suppliers of fiberscopes alsosupply borescopes. The major fiberscope/borescope supplier is Olympus. Other

suppliers are Machida, InstrumentTechnology, Richard Wolf, Circon ACMI,Schott Fiber Optics, and Lenox Instrument.Most of these companies are foreign owned,though many do some sort of assemblyand/or manufacturing in the U.S. to be ableto bid on government contracts.

Video probes use a miniature videocamera at the end of a cable to conductinspections. Welch Allyn is the leadingsupplier and first introduced the device toindustry in the 1980s. Other suppliersinclude Olympus, Visual InspectionTechnologies, Instrument Technology, andFibertron.

Diffracto holds the patent on D-Sight.The company has delivered 10 D-SightAircraft Inspection Systems (DAIS) tocustomers in North America and Europe.

Equipment suppliers of robots andcrawlers have concentrated most of theirmarketing on uses in hazardous wasteinspection, nuclear power plants, offshoreoil platforms, power plant inspections, andsewer inspections. The main use of this typeof equipment is for inspection of pipelines.Suppliers include REMOTEC, Benthos,Visual Inspection Technologies, PLSInternational, CTS Power Services, RacalSurvey, Cues, RS Technical Services, andPearpoint.

Laser shearography has been used toinspect engines and airframes of aircraft.Most often this technique is used to inspectcomposite materials for voids, delaminations,and unbonds. Laser Technology dominatesthe laser shearography market. They holdkey patents in this area and have primarilyfocused on the inspection of composite partsof military aircraft, though crossoverapplications into commercial aircraft, medical


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implants, and other components areanticipated.

The major suppliers of remote videomicroscopes are Japanese. The two keyplayers are Moritex and Keyence. One ofthe few North American companies involvedin the field is Infinity Photo-Optical.

Rem otely oper ated vehic les a re us ed in nuc lear power plan ts an d off shore dril lingpla tform insp ectio n. Mo st ar e con troll edvia an a ttach ed ca ble. Price s on these sys tems range from $20K to $ 200K. Equ ipmen t sup plier s inc lude R.O.V .Tec hnolo gies, Bent hos, Inter natio nalSub marin e Eng ineer ing, and D eep O ceanEng ineer ing.

6.1.2 Industry OutlookVisual/optical methods are extensively

used in jet engine inspection, which makesthem particularly sensitive to DoDaerospace shipments. This market area isexpected to continue to decline as budgetcutbacks ensue. Military aerospace productexports have also declined. And, with thedecline in the DoD aircraft force structure,this will also contribute to a decreasingnumber of jet aircraft and engines needing tobe inspected.

NASA, on the other hand, is looking toexpand its use of optical inspection, andplace less emphasis on their magneticparticle and liquid penetrant testing. This isdue to concerns about disposing of liquidwastes and eliminating the use ofchlorofluorocarbons used in pre-cleaningsteps. The environmental cleanup ofweapons facilities has actually increased thedemand for inspection robots and crawlers.

The commercial aircraft industry hasbeen a growth market for visual inspection

technologies, though this industry hasdeclined slightly in recent years. And, withair carriers consolidating, many havecombined their maintenance depotoperations and hence have a surplus ofoptical equipment.

As the aerospace industry continues touse more composite materials, the need toinspect multi-layer laminated structures willincrease. This will likely prove to be agrowth market for remote videomicroscopes, which are used to inspectairframes and airfoil surfaces for corrosion aswell as inspecting composite parts forimpact damage.

The shipbuilding industry is on thedecline, as is the budget for repair/modernization of existing ships.

The automotive industry will continue tobe a growth market for the visual inspectiontechnologies. The Big Three use remoteoptical inspection on their production line,and with the increased emphasis on qualityand reduction of defects, the techniques willbe used even more extensively.

The chem ical/ petro chemi cal i ndust ry is als o a h uge m arket for remot e opt icalins pecti on te chnol ogies . The se te chniq uesare used exte nsive ly at plan ts to insp ectins ide t anks, stru cture s and pipi ng. P ipecra wlers havi ng vi sion capab ility comb inedwit h ult rason ic ca pabil ities are in hi ghdem and. Remot e opt ical vehic les a re be inguse d mor e fre quent ly to insp ectund erwat er pi pelin es an d pla tform s. Th isis due i n par t to advan ces t hat h ave b eenmad e at LLNL to ov ercom e the atte nuati onlim itati ons e ncoun tered with floo d lam ps.

The electronics industry will also prove tobe an expanding market for visual inspectioncapabilities such as remote video microscopes


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and microboroscopes. These techniques areused to inspect such components as electronicassemblies and computer disk drives.

Another growth industry is utilitieswhere remote optical inspection techniques,such as video probes and remotely operatedvehicles, are predominant.

As advances are made in the field ofvisual inspection technologies, the market forthese technologies is expected to expand asthese technologies become more commonlyaccepted and can be demonstrated to savetime and minimize risk.

6.2Eddy Current

Testing using eddy currents began in the1930s. This technology is usually used inthe inspection of metals but can be appliedto any conducting sample. Eddy currenttesting is used for in-line production testingof metal bar, tubing and wire; in-servicemaintenance inspection of components inthe field and in re-work facilities; and gaugingthe thickness of layers. Most militarydepots have this capability, and it is quitecommonly used in the inspection of aircraft.

6.2.1 Equipment SuppliersThere are a handful of major suppliers.

Zetec is considered the largest supplier andprimarily focuses on the nuclear steamgenerator, aerospace and automotive markets.Magnetic Analysis is in the tube, bar and wireproduction inspection area. Foerster, asubsidiary of the German company InstitutDr. Foerster, deals in the tube-bar and wireinspection; aerospace and automotive fields.This company has a marketing agreement withUniWest to sell its equipment to the aerospaceindustry. Other suppliers include thefollowing:

• Stavely – aersospace

• K.J. Law – automotive

• Hocking (based in the UK with itsequipment distributed in the U.S.exclusively by Krautkramer Bransom) –aerospace and automotive

• UniWest- aerospace.

6.2.2 Industry OutlookFor years, the industrial base for this

technology area consisted of small com-panies. Several of these companies wereacquired by larger companies as theythrived. But, because the outlook for thistechnology is not considered high-growth,some of the large companies who made theseearlier acquisitions have divested themselvesof this business area.

Because the eddy current users demand ahigh level of support, overseas companieshave had to establish a North American sub-sidiary to gain market share. Many are act-ively pursuing export markets due to slug-gish domestic sales. Recent advancementshave made the eddy current equipment lessdependent on operator interpretation and,thus, more amenable to automated testing.

Eddy current technologies are anestablished process control method in anumber of industries and are displacing otherNDT methods in a number of areas due toenvironmental concerns. The technology isalso used extensively in maintenanceinspections of aircraft, pipelines, andchemical process plants, among other areas.

One potential growth area for eddy currenttechnologies is with NASA, which isevaluating replacing its penetrant inspectionwith eddy current testing. The inspection ofairbag components is also considered anexpanding market as is the automotiveindustry, which uses eddy current extensively


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for numerous applications. The chemical/petrochemical industry is another major end-user of eddy current testing, especially fortesting tubing for wall thinning. Eddy currentinspection will continue to play a crucial rolein the in-process inspection of milledcomponents, such as wires, tubes and bars. Itis also critical in the high speed inspection ofammunition and grenades for cracks andcorrosion. And this technology plays a majorrole in a number of coating and finishingindustries.

The utility industry could prove to beanother significant market for eddy currentequipment providers. Electric utilities areincreasing their level of NDT inspection due

to regulatory changes that are forcing theindustry to restructure in a new competitiveenvironment. The increased competition iscausing the utilities to look to ways toextend power plant service intervals andslash operating budgets. The industry istargeting faster, more efficient ways toconduct inspections. The nuclear powerindustry is also stepping up its NDEinspections due to safety considerations intheir aging facilities. In addition, eddycurrent technologies are the primaryinspection technique of steam generatortubing in pressurized water reactors.

6.2.3 UltrasonicsThe testing of the propagation of sound

in solids dates back to 1808. The inventionof the ultrasonic reflectoscope in 1940 led tothe development of modern ultrasonic NDEequipment. The base consisted of smallcompanies, several of which were acquiredby larger companies as the market for theseproducts grew. Ultrasonic technologies areused in flaw detectors, thickness gauges, andbond testers.

6.2.3.1 Equipment ProvidersMcDonnell Aircraft, a unit of

McDonnell Douglas (now Boeing), is amajor supplier of ultrasonic scanningsystems. The company markets the MAUSsystem and mainly focuses on the aerospacesector. One area of concentration is oncomposite aircraft structures. Other majorsuppliers include:

• Panametrics – aerospace,microelectronics

• ABB Amdata – power plants

• Sonix – acoustic microscopy formicroelectronic/materials applications

• Tecrad - power plants


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• IRT (an Israeli company) – aerospace, utilities

• SAIC Ultra Image (incorporates IRT electronics and scanners into its product line) – aerospace, ships, subs, utilities, and petrochemical

• Sonoscan – acoustic microscopy for microelectronic/materials applications

• Tektrend (Canadian company) – aerospace, utilities, research into new techniques (e.g., guided wave ultrasonics).

Major suppliers of ultrasonicinstruments and transducers for flawdetectors and thickness gauges areKrautkramer Branson (owned by EmersonElectric), Panametrics, Staveley, ABBAmdata, NDT Systems, and StressTel(owned by Emerson Electric).

6.2.3.2 Industry OutlookThis technology is presently not

considered a high-growth industry, whichhas led to the divestiture of some of theseearlier acquisitions. As with eddy currentproviders, sluggish domestic markets haveled suppliers to pursue exports. Recentadvancements have made the equipment lessdependent on operator interpretation andmore amenable to automated testing.Because this technology area is electronics-based, advancements and price/performanceimprovements in microelectronics andcomputer technology enhance the state-of-the-art of this technology.

Several industries are now usingultrasonics in process control. Thetechnology is also used extensively inmaintenance inspections of aircraft,pipelines, chemical process plants, and

power plants, among other areas. As is thecase with eddy current technologies,ultrasonic technology is displacing otherNDT methods in a number of areas due toenvironmental concerns.

Within the large ultrasonic systemsmarket, a shakeup has occurred with LKTool, Rolls –Royce MatEval and NDTSystems withdrawing from the NorthAmerican market and Automated InspectionTechnologies folding. There are a number ofreasons for this upheaval: 1) the companiescould not reduce their costs and remainprofitable due to the high investment andfixed costs incurred, 2) the reduction inmilitary aircraft procurement, 3) the slow-down in aircraft orders, and 4) the hugeupfront capital investment required frombuyers, causing them to hesitate on makingacquisitions of this nature.

The aircraft industry is considered anex- market for ultrasonics due to its increased use of composites. And, the AirForce continues to use ultrasonic testing inits Retirement for Cause program to inspectjet engine parts for cracks. The Air Forcealso continues to use large ultrasonic sys-tems for maintenance inspection of agingaircraft. As proven at the FAA’s NationalAging Aircraft Center, ultrasonics can nowbe used in the maintenance inspection oftee-caps.

Ultrasonic systems also play a majorrole in the inspection of high-spaceequipment, especially since the Challengerspacecraft tragedy. These systems are usedextensively to inspect rocket motors(previously only inspected by radiography)and propellant liners.

In the automotive arena, the inspectionof airbag inflators is considered to be an area


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of business expansion for ultrasonicsystems. Ultrasonic systems are being usedmore frequently in the area of processcontrol in high-volume batch processes,particularly for flaw detection, fluid levelmeasurement, and thickness measurement.It is used for tire inspections as well.

Ultrasonic systems are used extensivelyin the chemical and petrochemical industry,especially to inspect tubing wall thickness.New uses for ultrasonic systems arebeginning to be developed in the utilitiesindustry, especially in regards to steamgenerator testing. Mobile ultrasonic units arealso finding niches in the nuclear powerplant industry inspecting for intergranularcracking.

These systems also have a market in themetals industry where they are used toinspect pipes and tubing coming off theproduction lines for flaws and thickness.

Ultrasonic testing is used to inspect railsections during the manufacturing process aswell as for maintenance on the railbed. Thistechnology is also being researched for theinspection of railroad wheel rims. Atpresent, approximately one million wheelsare replaced annually in North America aspart of routine maintenance. Thesereplacements could be avoided by the use ofstepped up ultrasonic inspections measuringfor residual stress.

6.2.4 RadiographyRadiography is the first method of

internal visualization to be adapted to NDEin the 1930s. Film based radiographyequipment and film are considered matureproducts, making it difficult for suppliers todevelop niche markets since buyers treat theproducts as commodities rather than uniquedevices. The primary radiographic market is

medical. This technology is in directcompetition with advancing ultrasonic andeddy current technologies.

6.2.4.1 Equipment ProvidersThe number of major radiographic film

suppliers has decreased from four to three –Agfa, Fuji, and Kodak. Competition is fierceamong the remaining film suppliers targetinga shrinking market.

Major X-ray equipment suppliers areLorad, Pantak, Philips, Seifert, Andrex, andBateau.

Suppliers of real-time radiographysystems are Nicolet Imaging Systems (theleader), LumenX, Philips, FeinFocus, NDTMarketing, Lixi, Glenbrook Technologies,CR Technologies, SAIC, and LockheedMartin.

Major suppliers of computedtomography systems are:

• Hewlett-Packard – electronics

• ARACOR – rocket motorinspections

• Scientific Measurement Systems –industrial applications

• Bio-Imaging Research – flawdetection.

6.2.4.2 Industry OutlookThe film-based market has been under

pressure from military cutbacks andcorporate restructurings. Competition hasalso increased in the early 1990s whensurplus radiography equipment becameavailable and competed with new equipment.Film use is declining with the emergence ofreal-time radiography and user concern withthe environmental impacts of filmprocessing. In addition, this technology areaalso must compete against continual


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advancements in the field of eddy currentand ultrasonic technologies.

The non-film based radiography markethas also declined due to military cutbacks,which has lessened the demand for aerospaceand ordnance inspection. Suppliers havebranched out to other commercial marketssuch as the automotive and electronicsindustry to shore up their marketplacestance. The development of portableradioscopic systems has opened up thetechnology for use in field inspections ofpipelines and aircraft. And new applicationsin process control are emerging. Thistechnology is being continually enhanced dueto advances being made in the area of digitalelectronics and computers.

The c omputed to mography m arket hasalso suffered d ue to mili tary cutba cks, aswell as commerc ial custom ers’ desir e forlower prices an d faster p erformance . TheNavy has purcha sed six sy stems for theinspe ction of t heir Tride nt II miss iles,thoug h future p rocurement s are notantic ipated in the near f uture. Hil l Air Forc eBase also procu red a numb er of syst ems forthe i nspection of rocket motors, bu t again,the n eed in the near futu re for mor esyste ms is cons idered lim ited. The declinein de fense proc urements h as led CTsuppl iers to de velop new CT product s forthe c ommercial market, ma inly for u se inthe p roduction process. T hese syste ms areconsi derably sm aller than the large DoDsyste ms and, he nce, sold at a much reducedcost ($500K as compared t o multi-mi lliondolla r). Emergi ng applica tions for computedtomog raphy syst ems includ e metrolog y,rever se enginee ring, and rapid prot otyping.

Film radiography continues to be used inroutine inspections of metal parts in militaryaircraft and missiles. However, film

radiography has suffered a decline in otheraspects of military aircraft inspection, suchas inspection of wing fuel tanks of militarycargo aircraft. The military is now usingeddy current testing to find cracks in weepholes of these fuel tanks.

There is some question about what willhappen to the Sacramento Air LogisticsCenter’s radioscopic system upon theclosing of McClellan AFB in 1998. It isexpected that this $12M system will eitherbe sold to a private operator or maintainedby the Air Force at some other locations.

Commercial aircraft inspection during themanufacturing process is a huge market areafor radiographic testing. The trend in in-service inspections of commercial aircraft istoward use of advanced nondestructiveinspection technologies, such as computedradiography systems. On the other hand, theuse of film radiography for in-serviceinspections is declining.

Film radiography still has a niche marketin the inspection of warheads where thistechnology can be applied to inaccessiblelocations that cannot use real time systems.Real time radiography systems are usedquite extensively for inspecting largeordnance such as artillery shells. And, withthe end of the cold war, an increased need forthese systems has occurred to provide forthe safe disassembly of warheads. Neutronradiography is used to examine ordnancedevices containing hydrogenous explosive orpropellant in closed metal casing.

Film radiography is used in theshipbuilding area for a number ofapplications involving the inspection ofinaccessible components of ships andsubmarines.


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In the automotive arena, the inspectionof airbag components is considered to be anarea of business expansion for radiography.Radiography also is used extensively in theinspection of production castings.

The electronics market is a majorbusiness base for real-time radiographytechniques. It is used in the inspection ofsurface mounts, multi-layer circuit boards,and semiconductor packaging. Filmradiography is also still being used for suchapplications as failure analysis.

Film radiography is used in utilities forweld inspection and corrosion monitoring,among other applications. Considering theaging of the nuclear power plants and therestructuring and increased competition inthe electric utility industry, stepped upinspections of these systems are anticipated.

The metals industry is another majormarketplace for radiography systems.Inspections include pipes, tubing, and welds,to name a few components.

The railroad industry continues to be amajor market area for radiography systemsin regards to the inspection of railbeds andrailroad tank cars. Though film radiographyis primarily used, the industry is examiningfilmless radiography for its potential toreduce costs and environmental concerns.

Another anticipated growth market forradiography systems is in the medical field,inspecting such medical devices as artificialhearts, implants, and pacemakers during theassembly process.

6.2.5 ThermographyA thermography system will generally

consist of heat sources (lamps or flashlamps), heat measurement devices (infraredcameras), and image/data processing and

analysis equipment. Thermography as aninspection technology compares knownimages of non-damaged structure withimages of the inspected structure to identifyareas requiring further, more quantitativeexamination.

6.2.5.1 Equipment SuppliersThe industrial base for thermography

consists of camera suppliers, systemintegrators and service providers. The largestDoD/DND suppliers of infrared systems areLockheed Martin, Texas Instruments, andHughes. At present, they are not focusing onthe NDE market; however, should the NDEmarket develop, they will in all likelihoodplay a more prominent role.

The primary suppliers of cameras areAmerber Electronics (a subsidiary ofRaytheon), Cincinnati Electronics,Mitsubishi, and Inframetrics. Currentsystem integrators are Bales Scientific,EG&G Hudson, and Graseby Infrared.

Thermal Wave Imaging and Wayne StateUniversity are primary service providersattempting to create a market for thermaltechniques for NDE. They hold most of thepatents for the pulsed thermal imagingtechnique.

6.2.5.2 Industry OutlookThermography suppliers are not

dependent upon the NDE/NDT sector.Other major markets for this technology arepredictive maintenance, quality and processcontrol, R&D, night vision, law enforcement,aircraft landing guidance, and biomedical andautomobile drivers’ aids. Expansion of thethermography market is somewhathampered by its high equipment prices, lackof user training, and need for well-defined,established procedures. Although, thedecrease in prices of focal plane arrays is


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expected to help expand use ofthermography into other market areas.

6.3Summary

The industry outlook for each of thesetechnologies varies as does the industrial basesupporting development of them, though noneof these technologies is dependent upon thecorrosion detection technologies field for itslivelihood. However, the NDE/NDTequipment suppliers are very amenable tocustom adapting their equipment for specificapplications for a fee.

The industrial base for visual, ultrasonic,and eddy current equipment is relativelystable.

The base for film-based radiographyequipment has been dealt some setbacks inrecent years as film use is on the decline withthe emergence of real-time radiography,military cutbacks, and user concern withenvironmental impacts of film processing. Thenumber of major radiographic film suppliershas decreased from four to three, withcompetition fierce among those remainingfighting for market share in an ever shrinkingmarket.

Non-film based radiography suppliersmarket is in a state of flux. The market forradioscopy systems has declined due tomilitary cutbacks. However, in response tothis, suppliers have branched out to othercommercial markets such as the automotiveand the electronics industries to shore uptheir marketplace stance. And, with thedevelopment of portable radioscopicsystems, new uses for this technology haveopened up, such as in-field inspections ofpipelines and aircraft.

The number of thermographic equipmentand service providers is expanding from a

handful to a larger number as the technologymatures.

7. Conclusions RegardingFacilitators Enabling MoreWidespread Use of CorrosionDetection Technologies

The following sections describe thefacilitators in place to enable furtherwidespread use of corrosion detectiontechnologies that we have describedthroughout the course of this report. Thefacilitators are not intended to be all-inclusive but rather pinpoint the mostprominent ones we identified through thisstudy.

7.1Heightened Awareness

Due to the 1988 Aloha Airlines incidentand the Military Forces’ need to extend theservice life of military systems three to fourtimes their original design life, there isheightened awareness to the issue ofcorrosion and how it is a key contributor tosystem failures and a driving factor in termsof safety, downtime and costs. The FAAhas put in place a number of policydirectives aimed at the early detection andcorrection of corrosion problems. TheMilitary Forces have all stepped up effortsto prevent and control corrosion and arekeenly aware that in order to meet theirreadiness goals, they need to effectivelydetect and reduce the effect of corrosion ontheir defense systems. This need has beenunderscored by shrinking defense budgets,reduced procurements of new equipment,and increased reliance on modifications andupgrades to current systems. Corrosion hasbeen cited as one of the largest cost driverseffecting life cycle costs.


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7.2Established Working Groups

There are a number of establishedassociations and working groups addressingthe issue of corrosion, both within NorthAmerica and internationally. These includethe National Association of CorrosionEngineers, the Nondestructive TestingInformation Analysis Center, and theCanadian Nondestructive TestingAssociation. The U.S., Canadian andAustralian Governments also coordinate ontheir research into the field of corrosiondetection technologies via the CorrosionSub-Panel of the Technology Panel forAdvanced Materials (part of ProjectReliance).

The DoD, FAA and NASA have allestablished Aging Aircraft Programs toaddress corrosion issues. Similar research isbeing conducted in Canada by their NationalResearch Council, and in Australia by theirDefence Science and Technology Office.And, the Military Services have put in placecorrosion prevention and control programs.One of the goals of these programs is toadopt techniques that will enable moreefficient and cost-effective maintenanceinspections with fewer personnel.

A history of informal/formal technicalinteractions, information exchanges andcooperation exists between the DoD, FAAand NASA NDE/I programs. An example ofcooperation among federal agencies (ofwhich 14 participated including the AF,FAA and NASA) is the inter-government-agency working group on NDE/I, sponsoredby the White House Office of TechnologyPolicy (OSTP), Committee on Materials(COMMAT), to facilitate exchange ofNDE/I R&D results and promote jointplanning.

In addition, each of the Services conductsregular meetings to address corrosion issues.There have also been a number ofcoordinated meetings amongst and betweenthe U.S. Services, including the Joint ServiceWorking Group on Corrosion, as well aswith NASA and the FAA.

7.3New Emphasis on CostEffectiveness/Condition BasedMaintenance

As a cost savings strategy and toeliminate the need for unnecessarymaintenance, the Services are moving awayfrom routine maintenance where componentsare replaced based upon length of time inservice rather then real need. They areinstituting programs where components arereplaced based on their condition rather thanto conform to a given time-in-service. Thismove to condition based maintenance willprovide incentives to employ newer, moreefficient corrosion detection techniques sothat personnel will be better able to pinpointthe extent of their corrosion problems and itseffect on the structural integrity of thesystem.

8. Conclusions RegardingBarriers Affecting theWidespread Adoption ofCorrosion DetectionTechnologies

8.1General Barriers

There are several barriers to the widerappreciation of both the cost and importanceof corrosion in military systems and widersupport of R&D that will mitigate againstthe effects of corrosion. Only recently hasthe FAA sponsored an Aging AircraftProgram to address many of these concerns.


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Similarly, the U.S. Air Force has recentlyincreased the emphasis on these problemsby establishing an Aging Aircraft andSystems Office in the Aeronautical SystemsCenter at Wright-Patterson AFB, Ohio.However, other general barriers towidespread adoption of corrosion detectiontechnologies still exist.

8.1.1 Data Not Readily AvailableWhile collectin g data for this stud y, we

disco vered that recently publishedNDE/N DT and cor rosion det ection rep ortsare n ot showing up in DTI C, Dialog andother literatur e searches . Most of thepubli cations th at are in these data bases aredated . Also, in trying to gain data from thedepot /field lev el in rega rd to main tenanceand f ailure ana lysis and the role o fcorro sion in th e need to repair and replaceparts , it becam e apparent that this type ofinfor mation is not easily obtainabl e and,hence , is not g iven the v isibility it needs a tdiffe rent level s to ensur e that the serecur ring corro sion probl ems are ef fectivelycommu nicated an d that pro cedures ar e putin pl ace to rec tify the s ituation. This wastrue also in th e case of trying to quantifythe c ost of cor rosion to defense sy stems.There is no uni form equat ion or sta ndardecono mic develo ped of the elements fordeter mining the corrosion costs (th oughWarne r Robins h as release d a 1998 r eportthat breaks the se element s down for aircr aft). In a recent de velopment, TinkerAir F orce Base has just i nitiated ( late 1997) a pro ject to es tablish an Aging Air craftdatab ase.

8.1.2 Research Is DispersedThere are a number of different research

organizations conducting studies in the areaof corrosion detection technologies.

However, these groups are widely dispersedwithin DoD, DND, and the Australian DoD,reducing the visibility of the work beingperformed. Until recently, there was not agreat deal of coordination in the U.S.between these different groups, especiallyoutside of their respective Services thoughmore coordination has been initiated betweenthese groups as of late. The Canadian andAustralian organizations are more effectivein communicating their research resultswithin their countries, however all threecountries could benefit by increasedcoordination and sharing of findings betweentheir research communities. And, thereappears to be a disconnect between theoperators and the R&D community. TheR&D community is focusing on 6.1 and 6.2research whereas the operators areconducting program specific research, andthere does not seem to be effectivecommunication occurring between thedifferent groups.

8.2Technology Barriers

As described earlier, corrosion is itself acomplex phenomenon involving theinteraction of several different physicalprocesses. This complexity is the basis forthe wide array of technologies that areemployed to detect and characterizecorrosion. As would be expected, thetechnologies vary widely in reliability,accuracy, effectiveness and affordability.This section discusses the major barriers toquantitative improvements in the state of thetechnology.

8.2.1 Need for Newer Techniques NotWidely Recognized

The g eneral imp ression th at was for medthrou gh the num erous site visits co nductedby th e research team was that most users


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are s atisfied w ith curren t techniqu es.Comme rcial user s are wont to invest inaddit ional CD t echnology that canno t beclear ly justifi ed in econ omic terms . Overall, they are satisf ied that c urrent tec hnologiesand t echniques have serve d to preve ntcatas trophic lo sses. They are not i nformedas to the poten tial for r educed mai ntenanceand r epair cost s that cou ld be real izedthrou gh improve d corrosio n detectio ntechn ologies an d techniqu es. There isagree ment that the direct and indir ect costsof co rrosion ar e substant ial; there is notagree ment that these cost s can besubst antially r educed thr ough furth erinves tment in c orrosion d etection a ndquant ification technologi es and too ls.

8.2.2 NDE/NDT TechnologiesDeveloped for Applications Other ThanCorrosion

The f irst conce rn of stru ctural and mater ials engin eering has been the detectionand c haracteriz ation of d efects tha t can beadequ ately mode led and th ereforepredi cted; i.e. , cracks. NDE/NDTtechn ologies ha ve evolved to suppor t thescien ce of frac ture mecha nics, a di sciplinethat is now hig hly develo ped and qu iterelia ble in pre dicting th e life of complexstruc tures in k nown cycli c loadingenvir onments. T hese techn ologies, n otablyeddy current an d ultrason ic, have p rovenusefu l for dete cting and characteri zing themater ial loss c aused by c orrosion.Howev er, this i s after th e fact. Th edif ficul ty, a nd ne ar im possi bilit y, of pre dicti ng co rrosi on ha s poi nted the w orkin detec tion techn ologi es mo re to warddet ectio n of crack s tha n det ectio n ofmat erial loss due to co rrosi on. T he fa cttha t cor rosio n is cause d by many

int eract ing p roces ses c ontri butes to t hissit uatio n.

8.2 .3 Eff icien cy/Re liab i lity of Ne werTec hniqu es an d Cos t/Ben efits NotWel l Est ab lis hed

The tran sitio n of a new tech nolog yfro m lab orato ry to fiel d app licat ion i sdif ficul t. Th e gov ernme nt ha s bee n abl e toinv est i n som e of the m ore s ophis ticat edtec hnolo gies (such as n eutro n rad iogra phy)tha t wou ld be beyo nd th e rea ch of com merci al en terpr ises, airl ines forexa mple. Typi cally , a n ew te chnol ogy t hathas been deve loped in a labo rator y iscom merci alize d by a sma ll co mpany , oft ena s tart- up. B asica lly, the m arket place det ermin es th e suc cess or fa ilure of a par ticul ar te chnol ogy t hroug h cus tomer det ermin ation of t he co st-ef fecti venes s ofeac h new offe ring. With out s ome h istor ytha t wou ld su pport impr oved cost- eff ectiv eness , a n ew te chnol ogy o rtec hniqu e fac es a large hurd le to imp lemen tatio n on a wid e bas is.

8.2 .4 Saf ety C oncer ns Ab outRad iogra phy T echni ques

Alt hough radi ograp hy is perh aps t hemos t pre cise of th e cor rosio n det ectio n,and espe ciall y cor rosio n qua ntifi catio n,tec hnolo gies, it p resen ts th e mos t ser ioushaz ard t o the user s. In deed, in m anyjur isdic tions radi ograp hic f acili ties andope rator s are requ ired to be lice nsed. Fiel dope ratio n of x-ray equi pment requ ires thatper sonne l be kept at so me di stanc e fro mthe radi ation sour ces. The e mphas is on wor ker s afety and conce rns f or li abili tyjud gment s ser ve to impe de th e wid erimp lemen tatio n of radio graph ic te chniq ues.


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8.2 .5 The rmogr aphy Perce ived asNot Effe ctive or R eliab le

The rmogr aphy depen ds on oper atorint erpre tatio n of how a n ima ge of thestr uctur e in quest ion d iffer s fro m an image of a per fect or, a t lea st, a ccept able, str uctur e. Th us, f or ev ery i mage produ cedthe re mu st be a me ans t o com pare thatima ge ag ainst that of a simi lar u ndama gedstr uctur e. Co mbine d wit h the fact that the rmogr aphic imag es ar e som ewhat “fu zzy” compa red t o oth er im aging tec hniqu es (v isual , rad iogra phic, etc. ),man y use rs re main skept ical of th epre cisio n and reli abili ty of ther mogra phyas a cor rosio n det ectio n tec hnolo gy. T hisis due t o the fact that ther mogra phicima ges a re ca pture d by IR ca meras that aremad e up of an arra y of detec tors, each det ector cont ribut ing o ne pi xel t o the ove rall pictu re. T hus, IR ca meras have muc h low er re solut ion t han v isual pho togra phic proce sses (in m uch t he sa meway that a ph otogr aph h as mu ch be tterres oluti on th an a telev ision imag e).

8.2 .6 Hum an Fa ctors Limi tatio nsMuc h of the w ork i n ins pecti ng fo r

cor rosio n is repet itive and, in a word ,ted ious. For examp le, i nspec ting 25,00 0riv ets a nd fa stene rs on an a ircra ft us ing a nedd y cur rent probe can be a mind- numbi ngexp erien ce. T ake i nto a ccoun t tha t muc h ofthe work is d one i n awk ward locat ions andsom etime s und er ad verse envi ronme ntalcon ditio ns (d arkne ss, c old, etc.) Adde dtog ether , the prob lem o f ins pecti on fo rcor rosio n goe s wel l bey ond t hat o f jus t the tec hnolo gy of the sensi ng de vice and t hepro cessi ng of the infor matio n. It must inc lude an ar ray o f hum an fa ctors that will lim it th e ove rall effec tiven ess o f the ins pecti on pr ocess .

8.3Policy/Fiscal Barriers

8.3.1 Cost of Corrosion Difficult toCalculate

Determining the costs of corrosion in thelife cycle of a system is difficult to calculate.There currently is no baseline for this typeof measurement and no good cost data atpresent. Hence, the costs of corrosion arenot considered upfront in the acquisitioncycle since no benchmark for measuring theimpact of corrosion has been established. Inaddition, an effective cost/benefit analysis ofthe cost savings generated by implementing acorrosion detection technology is difficult toquantify.

8.3.2 Commercial Airlines/MilitaryHave No Economic Incentive toImprove Probability of Detecting MoreCorrosion

There is a para dox here i n that det ectionof mo re corrosi on means t hat more r epairwork must be do ne, and th at will in creasemaint enance cos ts. This i s because theFAA a nd militar y maintena nce guidel inesare r elatively narrow. Th ese guidel ines say,in es sence, tha t any corr osion dete ctedmust be correct ed. The go al of the airlines,then, is to mai ntain each aircraft at anadequ ate level while expe nding no m ore inmaint enance fun ds than is necessary .Perha ps the mos t attracti ve economi cincen tive to th e commerci al airline s wouldbe im proving th e producti vity of th einspe ction proc ess, there by reducin g thecost of mainten ance, assu ming that that canbe do ne without compromis ing the sa fetyor th e service life of th e aircraft . Withregar ds to the military, employing newtechn ologies co st money a nd, with t heairli nes, this cost must be weighed againstthe r eturn on i nvestment to the fac ility.Witho ut quantit ative cost data to s upport a


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decis ion to inv est in new technolog ies, mostof th e actual u sers would not incur such anexpen se at the depot leve l.

8.3.3 Cumbersome, Lengthy Processfor Emerging Techniques to Gain WideAcceptance/FAA-OEM Approval

Currently, Service Bulletins aredeveloped by the Original EquipmentManufacturers (OEMs) to deal with specificmaintenance problems. The FAA may issueAirworthiness Directives (ADs) to deal withproblems of a more urgent nature. ServiceBulletins receive FAA approval beforeissuance. Airline maintenance operationsmay implement the Service Bulletin throughan Alternate Means of Compliance (AMC).While the AMC is valid for the developingairline, it is not useable by anothermaintenance organization. In their quest tocontrol costs, airlines seek lower costalternatives to mandated inspection andrepair requirements. The approval processfor an AMC is lengthy and expensive. Thus,any new technology that has promise toimprove the inspection process and theproductivity of the maintenance operationfaces a not inconsequential approval cyclebefore it is generally accepted in thecustomer community.

8.3.4 Increased TrainingRequirements for Technicians to UseDifferent Technologies

Every different corrosion detectiontechnology will entail different trainingrequirements. Eddy current and ultrasonicsensors produce displays that require a highdegree of sophistication to properlyinterpret. Improved processing of newertechniques, such as stepped pulsed eddycurrent, provide c-scan images that are muchmore intuitive but still require expertinterpretation, especially in determining

when a particular threshold has beenexceeded and some expensive repair processis required. The range of technologies alsoexpands the knowledge required to interpretthe results. Thus, for a technician to beconsidered fully qualified in all areasnecessary to perform a complete corrosioninspection, many more skills are requiredthan before. Coupled with this is the factthat the number of trained NDT inspectorsis dwindling due to base closures andconsolidations and turnover at themaintenance level. Hence, the Services areexperiencing a loss of corporate memorythrough retirement of key personnel.

9. Recommendations of TheNational Research Council

The National Research Council, in 1997,published the report of a study, titled “Agingof U.S. Air Force Aircraft.” This studyexamines the entire range of topics affectingthe useful life of aircraft, including overloading,fatigue cracking, and corrosion. Therecommendations from this study relative tocorrosion detection technologies are highlyrelevant and illuminating, and apply to otherservices and other vehicles as well. The studyrecommendations for near-term research anddevelopment of corrosion detection and NDEtechnologies are summarized here:

Recommendation 19 (RegardingCorrosion and Stress Corrosion Cracking).Evaluate and implement methods to provideearlier detection of corrosion. Examples ofspecific tasks include:

• Investigation of environmentalsensors to allow aircraft maintenanceorganizations to anticipate whenconditions are likely to lead to corrosion


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• Evaluation of the applicability of the(US) Navy’s condition-based maintenanceprogram to (US) Air Force needs

• Development of techniques to locate,monitor, and characterize defects andchemical and physical heterogenenitywithin coatings.

• Development of techniques to locate,monitor, and characterize defects andchemical and physical heterogenenitywithin coatings.

Recommendation 30 (RegardingNondestructive Evaluation and MaintenanceTechnology). Apply automation and dataprocessing and data analysis technologies toaugment NDE tools to perform rapid, wide-area inspections. Examples of specifictechnologies that should be investigatedinclude:

• Effective automation of inspectionsand data collection equipment

• Imaging technology for improveddata analysis and interpretation

• Data integration for different testmethods for more complete and

quantitative interpretation of themeasurements

• Scanning and automated inspectionfacilities, especially for ultrasonic andeddy current methods

• Supportable instrumentation andequipment packaging that is convenientfor the operator and can survive thedepot environment

• Effective and focused engineering offield equipment capable of reproducinglaboratory and production testperformances.

The study identified critical NDEinspection needs for aging aircraft. The NDEinspection needs specifically related tocorrosion and not related to fatigue andcracking are summarized in Table 9-1.

These recommendations tend to supportthe conclusions and recommendations madeindependently in the NATIBO studyreported herein.

10. Recommendations


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10.1 Request the Corrosion Sub-Panel of TPAM Perform AddedCoordination Activities

To ensure the widespread disseminationof published reports on corrosion and thatinformation regarding corrosion detectiontechniques, advances, and implementationare effectively coordinated throughout theNDE/NDI community, the Corrosion Sub-Panel of TPAM should be approached abouttaking on the responsibility of:

• Coord inating an dpromo ting inter -actio n between theServi ces andident ifying com monprobl ems

• Establishing acentral repository ofreports and othercorrosion relatedinformation

• Improving reportdistribution

• Poolinginformation on systemfailures/corrosionproblem areas

• Establishing a Point ofContact database of technology experts (placed online and updated annually) so that timely consultation on specific corrosion related issues can be achieved.

If buy-in to thesecoordination activities is achieved, perhapsthis panel could enlist the aid of the NTIACto support these efforts.

10.2 Appoint Recognized Championsto Push for Corrosion Agenda andNew/Higher Fidelity Techniques

To ensure that the entirety of system lifecycle costs are considered in theprocurement process, identify and enlistmilitary champions to “market” the savingsto Programs/Program Managers from 1)

Table 9-1. Critical Corrosion NDE Inspection Needsfor Aging Aircraft.

Critical Need CandidateNDE Methods

Potential Techniques

Hiddencorrosion

Electromagnetic Pulsed eddy current

Multifrequency eddy current

SQUID technology

Eddy current

Thermal Time-resolved thermography

Radiography Energy-sensitive detectors

Microfocus real-timeradiography

Neutron

Ultrasonic Bubbler/scanning methods

Optical Boroscope

Corrosion inmulti- layerstructures

Electromagnetic Pulsed eddy current

Multifrequency eddy current

Radiography Real-time imaging

In-motion film

Ultrasonic Scanning (if gaps can bebridged)

Stresscorrosioncracking inthick sections

Ultrasonic Pulse echo

Scanning


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building into the design of the systemprotective measures to protect againstcorrosion and 2) including processes fordetecting corrosion problems early in asystem’s life cycle.

Additionally, the logistics communityshould be made aware of the importance ofcorrosion prevention and corrosion control inplanning for the life cycle support of systemsand in developing R&D requirements forextending the life cycle of weapon systems.These champions could emphasize theimportance of considering corrosion costs asan independent variable for determining lifecycle costs and push for establishingbenchmarks for measuring the impact ofcorrosion on the service life of a system. Inorder to better define these costs, thechampions could recommend that economicmodels be developed that address the costs ofcorrosion in the life cycle of the system andaddress the savings realized by planning forcorrosion detection upfront and detectingcorrosion early on in the system’s mainte-nance life. In addition, these champions couldstrive to establish an integrated approach totackling corrosion issues, ensuring thatIntegrated Product Teams consisting ofstructural engineers, NDE/NDI personnel andresearchers address these issues in a jointfashion.

10.3 Target Insertion/DemonstrationProgram

In order to demonstrate the benefitsderived from employing a certain corrosiondetection technology(s), a widely applicable,high payoff, dual use insertion/demonstrationprogram would be an ideal mechanism. Such

an insertion/demonstration program wouldhave to substantially meet the criteriadescribed in Section 1 earlier, i.e., apotentially powerful technology that hasdual-use application, can be supported by theindustrial base, and for which there is awindow of opportunity to mature.

A candidate for an insertion/ demon-stration program might be multi-sensor andmultiple data fusion, incorporatingautomation/robotics as deemed feasible.These suggestions support the findings ofthe National Research Council, and have metwith widespread backing from the membersof the NDE/NDI community. Industry andgovernment input would need to be solicitedto develop a DoD/DND/Australian-specificprogram that involves the fusing of as manyNDE techniques as possible. Researchers,developers and end-users would participatein the identification and selection process.

10.4 Streamline Process forInserting Newer Techniques into OEMMaintenance Procedures

The feedback from the researchcommunity through the OEMs back to theusers and operators of the systems shouldbe shortened. It should be possible toincentivize this process to rewardimprovements that can enhance systemreliability and extend the life of a systemwhile reducing the cost of inspection andrepair. The use of electronic updates toinspection and repair manuals can reduce theadministrative delay.

124M980175UNFINAL7A.doc.DOC

10.5 Increase Collaboration betweenthe Military Departments andUniversity NDE/NDT Departments onTraining

Training is usually an afterthoughtfollowing the development of newinspection technologies and tools. It should

be possible to procure integrated trainingalong with any new inspection tools. Suchtraining would be essential until each usingorganization was able to develop a core ofexpertise and thereby be able to conducttheir own training programs.

Appendix AAcronyms

M980175UNAppendices.doc.DOC

M980175UN A-1Final7a.DOC

Acronyms

AACE Aging Aircraft Center of ExcellenceAANC Airworthiness Assurance Nondestructive Inspection Validation CenterACE Airframe Condition EvaluationAD Airworthiness DirectiveAED Airframes and Engineering DivisonAFB Air Force BaseAFOSR Air Force Office of Scientific ResearchALC Air Logistics CenterAMC Alternate Means of ComplianceAMC Army Materiel CommandANDI Automated Nondestructive InspectorAR Army RegulationARL Army Research LaboratoryASIP Aircraft Structural Integrity ProgramATESS Aerospace and Telecommunications Engineering Support SquadronAUSS-V Automated Ultrasonic Scanning System - Generation FiveAVRD Air Vehicle Research DetachmentCARC Chemical Agent Resistant CoatingCASA Civil Aviation Safety AuthorityCASR Center for Aviation System ReliabilityCBI Compton BackscatterCBM Condition Based MaintenanceCCD Charge Coupled DeviceCDP Corrosion Data ProgramCFB Canadian Forces BaseCOTS Commercial-Off-The-ShelfCPAB Corrosion Prevention Advisory BoardCPC Corrosion Prevention and ControlCSIRO Commonwealth Science and Industrial Research OrganizationCT Computed TomographyDADTA Durability and Damage Tolerant AssessmentDBIR Dual Band InfraredDBIR CT Dual Band Infrared Computed TomographyDND Department of National DefenceDOC Department of CommerceDoD Department of DefenseDOE Department of EnergyDOT Department of Transportation


DSTO Defense Science and Technology OfficeDTIC Defense Technical Information CenterEC Eddy CurrentEIS Electrochemical Impedance SpectroscopyEMAT Electro-Magnetic Acoustic TransducerETRS Engineering Testing and Research ServicesFAA Federal Aviation AdministrationFMTV Family of Medium Tactical VehiclesFPI Fluorescent Liquid PenetrantFSMP Force Structural Management PlanGDP Gross Domestic ProductHFEC High Frequency Eddy CurrentIAR Insitute for Aerospace ResearchIMI Industrial Materials InstituteIR Infrared RedJPL Jet Propulsion LaboratoryKSC Kennedy Space CenterLBL Lawrence Berkeley LaboratoryLFEC Low Frequency Eddy CurrentLLNL Lawrence Livermore National LaboratoryLPI Liquid Penetrant InspectionLUS Laser Based UltrasoundMACS Multifunctional Automated Crawling SystemMAJCOM Major Operating CommandMARCORSYSCOM Marine Corps Systems CommandMAUS Mobile Automated ScannerMCT Microfocus Computed TomographyMED Multi-Element DamageMOI Magneto-Optic ImagingM P Magnetic ParticleNACE National Assocation of Corrosion EngineersNADEP Naval Aviation DepotNASA National Aeronautical and Space AdministrationNATIBO North American Technology and Industrial Base OrganizationNAVAIR Naval Air Systems CommandNAWC Naval Air Warfare CenterNDE Nondestructive EvaluationNDI Nondestructive InspectionNDISL Non-Destructive Inspection Standards LaboratoyNDT Nondestructive TestingNRCC National Research Council CanadaNRL Naval Research LaboratoryNSWC Naval Surface Warfare Center


NTIAC Nondestructive Testing Information Analysis CenterOEM Original Equipment ManufacturerPHNSY Pearl Harbor Naval ShipyardP M Program ManagerPOD/CL Probability of Detection/Confidence LevelPRI Physical Research Instrumentation, Inc.QETE Quality Engineering Test EstablishmentR&D Research and DevelopmentRMC Royal Military CollegeROI Return on InvestmentROV Remorely Operated VehicleRT RadiographyS&T Science and TechnologySBIR Small Business Innovative ResearchSDL Special Development LaboratorySML Structures and Materials LaboratorySPO System Program OfficeSQUID Superconducting Quantum Interference DeviceSSMD Ship Structures and Materials DivisionSwRI Southwest Research InstituteTACOM Tank Automotive CommandTDC Transportation Development CentreTFLM Tactical Fighter Logistics SquadronTPAM Technology Panel for Advanced MaterialTWI Thermal Wave ImagingUDRI University of Dayton Research InstituteUSAF United States Air ForceUSMC United States Marine CorpsUT UltrasonicWBCC Waterbourne Camoflauge CoatingWDCP Water Displacing Chemical PrservativesWFD Widespread Fatigue Damage


Appendix B

Bibliography

M980175UN B-1Appendices.doc.DOC

ID # Author Title Source/Citation

1 Adams, Tom Ultrasonic Inspection of CeramicBearings

Advanced Materials andProcesses

2 Agarwala, V.S., andAlan Fabiszewski

Thin Film Microsensors for Integrityof Coatings, Composites and HiddenStructures

NACE Corrosion/94 PaperNo. 342

3 Agarwala, Vinod In-Situ Corrosivity Monitoring ofMilitary Hardware Environments


4 Agarwala, Vinod S. Corrosion Monitoring Provided by NAWC-Patuxent River

5 Argonne NationalLaboratory

Argonne's Electrochemical NoiseProbe Differentiates Sustained,Localized Pitting Corrosion fromUniform Pitting Corrosion

ANL NACE ConferenceHandout

6 Argonne NationalLaboratory

Ceramic Coatings: OptimizationofCorrosion and Wear Resistance byIBAD

ANL NACE ConferenceHandout

7 Armistead, Robert A.and James H. Stanley

Computed Tomography: A VersatileTechnology


8 Army ResearchLaboratory

Surface Engineering of Materials(Information Sheet)

Provided by ARL

9 Army ResearchLaboratory

Surface Protection (Information Sheet) Provided by ARL

10 Bar-Cohen, Yoseph,et.al.

International NDT TechnicalCollaboration Using the Internet

WWW Download

11 Battelle Economic Effects of Metallic Corrosion in the United States. A 1995Update.

12 Beattie, Allan, et.al. Emerging Nondestructive Inspectionfor Aging Aircraft

DOT/FAA/CT-94-11

13 Bellinger, N.C., andJ.P. Komorowski

Damage Tolerance Implications ofCorrosion Pillowing on Fuselage LapJoints (Briefing)

1996 USAF StructuralIntegrity ProgramConference, San Antonio, TX

14 Bellinger, N.C., andJ.P. Komorowski

The Effect of Corrosion on theStructural Integrity of Fuselage LapJoints (Briefing)

1995 USAF StructuralIntegrity ProgramConference, San Antonio, TX



15 Bellinger, N.C., S.Krishnakumar andJ.P. Komorowski

Modelling of Pillowing Due toCorrosion in Fuselage Lap Joints

Canadian Aeronautics andSpace Journal, Vol. 40, No. 3

16 Bellinger, NicholasC., and Jerzy P.Komorowski

Corrosion Pillowing Stresses inFuselage Lap Joints

AIAA Journal, Vol. 35, No. 2

17 Bellinger, NicholasC., and Jerzy P.Komorowski

Implications of Corrosion Pillowingon the Structural Integrity of FuselageLap Joints

NASA-FAA Symposium

18 Beshears, Ronald D.,and Lisa Hediger

Radiographic Analysis of the TSS-1RConductive Tether

Materials Evaluation

19 Bigelow, Cynthia A.(editor)

FAA-NASA Sixth InternationalConference on the ContinuedAirworthiness of Aircraft Structures

DOT/FAA/AR-95/86

20 Bindell, Jeffrey B. Elements of Scanning ElectronMicroscopy


21 Bird, Kenneth W. andKirk Richardson

Zirconium for Superior CorrosionResistance


22 Birring, Anmol Corrosion Monitoring of UnderwaterSteel Structures

Corrosion Monitoring inIndustrial Plants UsingNondestructive Testing andElectrochemical Methods.ASTM STP 908, G.C Moranand P. Labine, Eds., AmericanSociety for Testing andMaterials, Philadelphia, pp.179-190.

23 Bobo, Stephen N. The Aging Aircraft Fleet: A Challengefor Nondestructive Evaluation

Review of Progress inQNDE, Vol. 9B

24 Boeing Corporation/American Airlines

Maintenance Procedure No. 26 forBoeing 727 Aircraft

American Airlines

25 Bray, Donald E., N.Pathak and M.N.Srinivasan

Residual Stress Mapping in a SteamTurbine Disk Using the LCRUltrasonic Technique




26 Burkhardt, Gary L.,et.al.

High Sensitivity/High ProductivityInspection of Aircraft Structure withAdvanced Eddy Current Probes(Information Slide)

Provided by SouthwestResearch Institute

27 Burleigh, Douglas D. Practical (Nontechnical) Aspects ofNDT, Using Thermographic NDT asan Example


28 Chiotakis, Michael T. Concepts of Real-Time Radiography Materials Evaluation

29 Cielo, P., X. Mal-dague, A.A.Deomand R. Lewak

Thermographic NondestructiveEvaluation of Industrial Materials andStructures


30 Committee on Agingof U.S. Air ForceAircraft

Aging of U.S. Air Force Aircraft:Interim Report

National Academy PressPublication NMAB-488-1

31 Connolly, Mark P. A Review of Factors InfluencingDefect Detection in InfraredThermography: Applications toCoated Materials

Journal of NondestructiveEvaluation, Vol. 10, Nos. 3

32 Cooke, Garth, et.al A Study to Determine the AnnualDirect Cost of Corrosion MaintenanceFor Weapon Systems and Equipmentin the United States Air Force

Warner Robins ALC

33 Costley, Jr., R.Daniel, Yves H.Berthelot andLaurence J. Jacobs

Fresnel Arrays for the Study of LambWaves in Laser Ultrasonics


34 Crawley, N.H., et.al. A Canadian Forces Perspective onAging Aircraft

Presentation at the First JointDOD/FAA/NASAConference on Aging Aircraft

35 De Luccia, J.J. The Corrosion of Aging Aircraft andIts Consequences

AIAA 32nd Structures,Structural Dynamics, andMaterials Conference

36 Diffracto DAIS:D Sight Aircraft InspectionSystem (Information Report)

Provided by Diffracto



37 Diffracto DAIS:D Sight Aircraft InspectionSystem. DAIS 250CV Field Trial


38 Diffracto DAIS:D Sight Aircraft InspectionSystem. Delta Report


39 Doruk, R. and R.L.Thomas

Technical Evaluation Report AGARD ConferenceProceedings 565, CorrosionDetection and Managementof Advanced AirframeMaterials

40 Drinkwater, Bruceand Peter Cawley

The Practical Application of SolidCoupled Ultrasonic Transducers


41 Dunn, D.S., N.Sridhar and G.A.Cragnolino

Long-Term Prediction of LocalizedCorrosion of Alloy 825 in High-LevelNuclear Waste RepositoryEnvironments

Corrosion, Vol. 52, No. 2, pp.115-124

42 Dunn, Darrell S.,Narasi Sridhar andGustavo A.Cragnolino

Effects of Surface ChromiumDepletion on the Localized Corrosionof Alloy 825 as a High-Level NuclearWaste Container Material

Darrell Dunn-SouthwestResearch Institute

43 Eichinger, BernadetteJ.

NSWC Carderock Division, In-Service Engineering Department-Code62 (Briefing)

44 Favro, L.D., et.al. Thermal Wave Imaging for AgingAircraft Inspection


45 Federal AviationAdministration

Federal Aviation AdministrationOffice of Aviation Research, ResearchProject Descriptions

Provided by Chris Smith

46 Federal AviationAdministration

National Aging Aircraft ResearchProgram

Provided by Chris Smith

47 Fisher, W.G., et.al. Laser Induced Fluorescence Imaging ofThermal Damage in Polymer MatrixComposites


48 Fitzpatrick, G.L.,et.al.

Magneto-Optic/Eddy Current Imagingof Subsurface Corrosion and FatigueCracks in Aging Aircraft

Review of Progress inQuantitative NondestructiveEvaluation, Vol. 15



49 Forney, Donald M.,and Dale E. Chimenti

Nondestructive Evaluation - Comingof Age

Encyclopaedia Britannica1986 Yearbook of Science andthe Future



50 Foster, Barbara andBarry Fookes

Image Analysis for Materials Science Advanced Materials andProcesses

51 Gans, Ronald R. andR.M. Rose

Crack Detection in ConductingMaterials Using SQUIDMagnetometry


52 Gieske, John H. Evaluation of Scanners for C-ScanImaging for Nondestructive Inspectionof Aircraft

DOT/FAA/CT-94/79

53 Glatz, Joseph Krypton Gas Penetrant Imaging - AValuable Tool for Ensuring StructuralIntegrity in Aircraft EngineComponents


54 Granata, Richard D.,John W. Fisher, andJames C. Wilson

Update on Applications of CorrosionCoulometers


55 Gray, Sheila andReza Zoughi

Dielectric Sheet Thickness Variationand Disbond Detection inMultilayered Composites Using andExtremely Sensitive MicrowaveApproach


56 Grewel, Dilawar S. Improved Ultrasonic Testing ofRailroad Rail for TransverseDiscontinuities in the Rail Head UsingHigher Order Rayleigh (M21) Waves


57 Hagemaier, D., B.Bates and A.Steinberg

On-Aircraft Eddy Current SubsurfaceCrack Inspection


58 Hagemaier, D.J.,A.H. Wendelbo, Jr.and Y. Bar-Cohen

Aircraft Corrosion and DetectionMethods


59 Hagemaier, D.J., P.R.Abelkis and M.B.Harmon

Supplemental Inspections of AgingAircraft


60 Hagemaier, Don andGreg Kark

Eddy Current Detection of ShortCracks Under Installed Fasteners




61 Hagemaier, Donald J. Aerospace Radiography-The LastThree Decades


62 Hagemaier, Donald J. Cost Benefits of NondestructiveTesting in Aircraft Maintenance


63 Hagemaier, Donald J. Effective Implementation of NDT intoAircraft Design, Fabrication, andService


64 Hagemaier, Donald J.and John Petty

Evaluation of Shims, Gaussmeter,Penetrameter, and Equations forMagnetic Particle Inspection


65 Harrison, D.J., L.D.Jones and S.K. Burke

Benckmark Problems for Defect Sizeand Shape Determination in Eddy-Current Nondestructive Evaluation

Journal of NondestructiveEvaluation, Vol. 15, No. 1

66 Heoppner, David W.,et.al.

The Role of Fretting Fatigue onAircraft Rivet Hole Cracking

DOT/FAA/AR-96/10

67 Hochheiser, RobertM.

Priceless Artwork Preserved with theHelp of NDT


68 Howard, Quincy The Applicability of Wide-AreaInspection Techniques on BoeingAirplanes

Provided by Quincy Howard,Boeing

69 Howard, Quincy The Role of New-Technology NDITechniques

Provided by Quincy Howard,Boeing

70 Humphries-Black,Hollis

Infrared Testing in Art Conservation Materials Evaluation

71 Hutchins, D., J. Huand K. Lundgren

A Comparison of Laser and EMATTechniques for NoncontactUltrasonics


72 Jin, Feng and F.P.Chiang

A New Technique Using DigitalSpeckle Correlation forNondestructive Testing of Corrosion


73 Johns HopkinsUniversity/Center forNondestructiveEvaluation

1997 CNDE Annual Report Provided by Dr. Bob Green,JHU/CNDE



74 Johnson, Richard E.,and Vinod S.Agarwala

Fluorescence Based Chemical Sensorsfor Corrosion Detection




75 Jones, Walter F. Air Force Program in Aging AircraftResearch

Presented at AirForce/FAA/NASACoordination Meeting

76 Kane, Russell D. Super' Stainless Steels Resist HostileEnvironments


77 Kane, Russell D. andRichard G.Taraborelli

Selecting Alloys to Resist Heat andCorrosion


78 Kaplan, Herbert IR Nondestructive Testing Speeds Up Photonics Spectra

79 Karpala, F., and O.L.Hageniers

Characterization of Corrosion andDevelopment of a Breadboard Modelof a D-Sight Aircraft InspectionSystem-Phase I

DOT/FAA/CT-94/56

80 Karpala, F., and O.L.Hageniers

Development of a D-Sight AircraftInspection System, Phase II

DOT/FAA/AR-95/15

81 Karpala, Frank, DaveWillie and JerzyKomorowski

NDI Data Organization Methodologyfor Life Cycle Management

Provided by NRC Canada

82 Kelly, R.G., et.al. Embeddable Microinstruments forCorrosion Monitoring


83 Komorowski, J.P.,D.L. Simpson andR.W. Gould

Enhanced Visual Technique for RapidInspection of Aircraft Structures


84 Komorowski, J.P.,et.al.

Quantification of Corrosion in AircraftStructures with Double PassRetroreflection

Canadian Aeronautics andSpace Journal, Vol. 42, No. 2

85 Komorowski, JerzyP., et.al.

Double Pass Retroreflection forCorrosion Detection in AircraftStructures


86 Kwun, H., J.J.Hanley and A.E. Holt

Detection of Corrosion in Pipe Usingthe Magnetostrictive SensorTechnique

SPIE Vol. 2459

87 Lepine, B.A. Air Vehicle Research SectionCorrosion Detection R&D Activities

Provided by Capt BrianLepine



88 Lerner, Yury andPaul Brestel

Ultrasonic Testing Predicts CastingProperties


89 Lord, Robert J. andMark S. Ruesing

Coatings Used in Combat Aircraft Materials Evaluation

90 Louthan Jr., M.R.and M.J. Morgan

Some Technology Gaps in theDetection and Prediction ofHydrogen-Induced Degradation ofMetals and Alloys

Journal of NondestructiveEvaluation, Vol. 15, Nos. 3/4

91 Maldague, X., P.Cielo and C.K. Jen

NDT Applications of Laser-Generated Focused Acoustic Waves


92 Maxfield, B.W., A.Kuramoto and J.K.Hulbert

Evaluating EMAT Designs forSelected Applications


93 Mayton, Donna J.,Douglas A. Ourslerand James W. Wagner

Magnetic Pressure Stressing of LapJoints: Modeling and ExperimentalVerification


94 McDonnell Douglas MAUS III Mobile AutomatedScanner

Provided McDonnell Douglas

95 McDonnell DouglasAerospace

NDE Method Development forCorrosion Detection

Provided by McDonnellDouglas Aerospace

96 Michaels, Thomas E.and Barry D.Davidson

Ultrasonic Inspection Detects HiddenDamage in Composites


97 Monchalin, J.-P. andR. Heon

Laser Ultrasonic Generation andOptical Detection with a ConfocalFabry-Perot Interferometer


98 Moran, George andJack Spanner

The Importance of Standardization Materials Evaluation

99 Moulder, J.C., et.al. Scanned Pulsed Eddy CurrentTechnique for Characterizing HiddenCorrosion and Cracking in Airframes(Briefing)

Provided by the Iowa StateUniversity Center for NDE

100 Nagy, P.B., A.Jungman and L. Adler

Measurements of BackscatteredLeaky Lamb Waves in CompositePlates




101 Nagy, Peter B. Leaky Guided Wave PropagationAlong Imperfectly Bonded Fibers inComposite Materials




102 NAWC-PatuxentRiver

Trivalent Chromium Solutions forApplying Chemical ConversionCoatings to Aluminum Alloys

Provided by NAWC-Patuxent River

103 Nieser, Donald E. Oklahoma City Air Logistics Center(USAF) Aging Aircraft CorrosionProgram

Provided by Don Nieser

104 Owen, Roger High Energy Radiography Using a 6MeV Portable Linear Accelerator


105 Patton, Thadd C.,and David K. Hsu

Doing Focused Immersion UltrasonicsWithout The Water Mess

Provided by the Iowa StateUniversity Center for NDE

106 Pautz, John F. andKlaus Abend

Automated Magnetic Particle Testing Materials Evaluation

107 Pearlstein, Fred, andVinod Agarwala

Trivalent Chromium Treatment forAluminum - Corrosion Resistance andPaint Adhesion


108 Peterson, Michael L.and M.E. Ellis

Advanced Visualization forInterpretation of C-Scan Data


109 Placzankis, Brian E.,et.al.

Evaluation of Non-ChromateConversion Coatings on AluminumArmor Alloys


110 Raj, Baldev, K.Viswanathan andC.G. Krishnadas Nair

A Report on Nondestructive Testingand Evaluation in India


111 Riley, John N.,Emmanuel P.Papadakis andStephen J. Gorton

Availability of Training in VisualInspection for the Air TransportIndustry


112 Rogerson, Allan Current ISI and MonitoringTechnologies in European EnergyIndustries


113 Rose, J.L., et.al. Hidden Corrosion Detection withGuided Waves




114 Rose, J.L., P. Karpurand V.L. Newhouse

Utility of Split-Spectrum Processingin Ultrasonic NondestructiveEvaluation


115 Rose, James H.,Ronald A. Robertsand Frank J.Margetan

Time-Domain Analysis of UltrasonicReflection from Imperfect Interfaces


116 Rose, Joseph L. andAleksander Pilarski

Surface and Plate Waves in LayeredStructures


117 Rose, Joseph L., DaleJiao, and JackSpanner, Jr.

Ultrasonic Guided Wave NDE forPiping


118 Roth, Don J., et.al. Commercial Implementation ofNASA-Developed Ultrasonic ImagingMethods via Technology Transfer


119 Rowland, S.N., G.Burkhardt and A.S.Birring

Electromagnetic Methods to DetectCorrosion in Aircraft Structures

Review of Progress inQNDE, Volume 5B

120 Sandor, B.I., D.T.Lohr and K.C.Schmid

Nondestructive Testing UsingDifferential Infrared Thermography


121 Schmidt, C.G., et.al. Characterization of Early Stages ofCorrosion Fatigue in Aircraft Skin

DOT/FAA/AR-95/108

122 SEMCOR SEMCOR's Expertise in CorrosionControl

Provided by SEMCOR

123 Shagam, Richard N. Light Shaping Diffusers for ImprovedVisual Inspection of Aircraft

DOT/FAA/AR-95/32

124 Shepard, S.M. Issues and Problems in IR ImageInterpretation

Predictive MaintenanceTecnology NationalConference

125 Shepard, Steven M. Thermal Wave Imaging for NDI ofPipelines, Storage Tanks, and PressureVessels

ASNT International Chemicaland Petroleum IndustryInspection Technology(ICPIIT) IV Conference



126 Singh, A., R. Kingand R.L. Brackett

Economic Model to Determine theBenefits of Inspecting SteelWaterfront Structures

Review of Progress inQNDE, Volume 3B

127 Singh, G.P. Inspection of Corroded Material Materials Evaluation

128 Singh, G.P. and GaryRutherford

Corrosion/Erosion Detection Using B-Scan Imaging


129 Sison, Miguel, et.al. Acoustic Emission: A Tool for theBridge Engineer


130 Skeie, K. and D.J.Hagemaier

Quantifying Magnetic ParticleInspection


131 Skinner, Liz Thermal Wave Imaging Inc.: HeatVision For Sale

Technology TransferBusiness

132 Smith, Chris andPatrick L. Walter

Revisiting the Aging AircraftNondestructive Inspection ValidationCenter - A Resource for the FAA andIndustry


133 Smith, ChristopherD.

Federal Aviation AdministrationAircraft Inspection Research andDevelopment Programs

Chris Smith-FAA TechnicalCenter

134 Spencer, Floyd W. Visual Inspection Research ProjectReport on Benchmark Inspections

DOT/FAA/AR-96/65

135 Spencer, Floyd, andDonald Schurman

Reliability Assessment at AirlineInspection Facilities. Volume III:Results of an Eddy Current InspectionReliability Experiment

DOT/FAA/CT-92-12, III

136 Sridhar, Narasi andDarrell Dunn

In-Situ Study of Salt Film Stability inCorroding Pits by RamanSpectroscopy (Information Slide)

Provided by SouthwestResearch Institute

137 Stubbs, David A. andLarry P. Zawada

Detection of Porosity in GlassCeramic Matrix Composites Using anUltrasonic Multiple-Gate C-ScanTechnique




138 Thermal WaveImaging, Inc.

Company Information Pack Provided by Thermal WaveImaging

139 Thompson, R.B. Laboratory Nondestructive EvaluationTechnology for MaterialsCharacterization


140 TPL, inc. Nondestructive Evaluation (includesTPL, inc. product guides)

Provided by TPL, Inc.

141 Truchetet, Fred, et.al. Automatic Surface Inspection ofMetal Tubes by Artificial Vision


142 Tullmin, M., P.R.Roberge and M.A.Little

Aircraft Corrosion Surveillance in theMilitary


143 Tullmin, M., P.R.Roberge and M.A.Little

Sensors for Aircraft Corrosion -Review and Future Developments


144 Twomey, Michael Inspection Techniques for DetectingCorrosion Under Insulation


145 Wanhill, R.J.H, andJ.J De Luccia

An AGARD-Coordinated CorrosionFatigue Cooperative TestingProgramme

AGARD Report No. 695

146 Wei, Robert P., andGary Harlow

Corrosion and Corrosion Fatigue ofAirframe Materials

DOT/FAA/AR-95/76

147 Weischedel, HerbertR.

The Inspection of Wire Ropes inService: A Critical Review


148 Weischedel, HerbertW.

Quantitative In-Service Inspection ofWire Ropes


149 Willie, David J. andFrank Karpala

Proactive Aircraft Lap Joint CorrosionMaintenance Scheduling

Airframe FinishingMaintenance and RepairConference and Exposition.SAE Technical Paper 961247

150 Wong, B.S., et.al. Mechanical Impedance Inspection ofAluminum Honeycomb Structures




151 Airworthiness Directives - August1996

WWW Download -http://www.acflyer.mcgraw-hill.com/flightwatch/ADs9608.html

152 Detector Handbook Laser Focus World

153 Dry-Couplant Ultrasonics EliminatesContamination (Materials ProgressSummary)

Advanced Materials &Processes

154 Eddy Current Inspection Evaluatedfor Aircraft (Materials ProgressSummary)


155 Eddy Current Probe Operates DuringRolling Operation (Materials ProgressSummary)


156 Flux-Focusing Eddy-Current ProbeDetects Aircraft Cracks (MaterialsProgress Summary)


157 Heat-Pulse NDT Reveals FiberVolume Fractions (Materials ProgressSummary)


158 Metallic Corrosion Annually CostsU.S. $300 Billion (Materials ProgressSummary)


159 NDT of Jet Engines: An IndustrySurvey. Part One


160 NDT of Jet Engines: An IndustrySurvey. Part Two


161 NDT Systems Combined to DetectCracks and Flaws (Materials ProgressSummary)


162 NTSB Incident Report WWW Download -http://www.ntsb.gov:80/aviation/DCA/96A036.htm



163 Product Showcase: NondestructiveTesting Equipment




164 Product Spotlight: Acoustic Emissionand Vibration


165 Product Spotlight: Eddy CurrentTesting


166 Product Spotlight: Magnetic Particleand Liquid Penetrant Testing


167 Product Spotlight: NDT of Steel Materials Evaluation

168 Product Spotlight: Radiography Materials Evaluation

169 Product Spotlight: Ultrasonic Testing Materials Evaluation

170 Product Spotlight: Visual and OpticalTesting


171 Seek But Don't Destroy Machine Design

172 Sound Out Cracks in Ceramics andMetals (Materials Progress Summary)


173 Superconducting Tapes TestedUltrasonically During Heating(Materials Progress Summary)


174 Test Warns of Aircraft Cracks andCorrosion (Materials ProgressSummary)


175 X-Ray System Uses Miniprobes toDetect Corrosion in Pipes

Advanced Materials andProcesses, P. 13

176 X-Rays, Ultrasound, Optics GenerateMaps of Stresses (Materials ProgressSummary)



Appendix C

Points of Contact

M980175U C-1AppendixC.doc.DOC

Point of Contact Company Company Address Phone Fax E-mail

Last Name First Name Name Address City State/Prov. Zip Code Number Number Address

Agarwala Vinod Naval AirWarfare Center

Aircraft Div.,Code4.3.4A/Unit 5

Patuxent River MD 20670-1908 (301) 342-8002 (301) 342-8062 agarwala_vinod %[email protected]

Bar-cohen Yoseph JPL 4800 OakGrove Drive

Pasadena CA 91109-8099 (818) 354-2610 (818) 393-4057 [email protected]

Barton Andrew C.W. Pope &AssociatesPTY Ltd.

24 CallisternonClose

Warabrook Australia 2304 61 49 672788 61 49 601030 [email protected]

Beatty John US ArmyResearch Lab

AMSRL-WM-ME

APG MD 21005 (410) 306-0869 (410) 516-5293

Bennett Les Royal MilitaryCollege ofCanada

PO Box17000, StnForces

Kingston Ontario K7K 7B4 (613) 541-6000x6614

(613) 542-9489 [email protected]

Bevan Steve JacksonvilleNADEP

Code 4.3.4.2,Bldg 793

Jacksonville FL 32212 (904) 772-4516 (904) 772-4523 bevan%jx%[email protected]. mil

Boone Larry Quality Engi-neering TestEstablishment

Ottawa Ontario K1A 0K2 (819) 997-1392 (819) 997-2523

Bowles Susan DSTO Aus-tralia, Aeronau-tical and Mari-time ResearchLaboratory

G.P.O. Box4331Melbourne

Victoria Australia 3001 03626 7859 03 626 7087 [email protected]

Brassard Michel Tektrend 2113A StRegis Blvd,Dollard

Montreal Quebec H9B 2M9 (514) 421-1417 (514) 421-1487

Burke Stephen DSTO Aus-tralia, Aeronau-tical and Mari-time ResearchLaboratory

G.P.O. Box4331Melbourne

Victoria Australia 3001 61 3 626 7504 61 3 626 7087 steve.burke@ds to.defence.gov.au

Burkhardt Gary Southwest Re-search Institute

6220 CulebraRd

San Antonio TX 78228-0510 (210) 522-2705 (210) 684-4822 [email protected]




Bussiere Jean NRC Canada 75 de Mortagne Boucherville Quebec J4B 6Y4 (514) 641-5252 (514) 641-5106 jean.bussiere@ nrc.ca

Choquet Marc NRC Canada 75 de Mortagne Boucherville Quebec J4B 6Y4 (514) 641-5022 (514) 641-5106 [email protected]

Clark Graham DSTO Aus-tralia, Aeronau-tical and Mari-time ResearchLaboratory

P.O. Box4331, 506Lorimer StreetFishermensBend

Victoria Australia 3001 61 3 9626 7497 61 3 9626 7089 [email protected] v.au

Colling-wood

Michael NDE, CouglasProducts Divi-sion, BoeingCommercialAirplanceGroup

3855 Lake-wood Blvd.

Long Beach CA 90846 (562) 593-9949

Collins J. David NASA Ken-nedy SpaceCenter

DC-ICD-A JFK SC FL 32899 (407) 867-4438

Corcino Tony JacksonvilleNADEP

Code 4.3.4.1,Bldg 793

Jacksonville FL 32212 (904) 772-4516x136

(904) 772-4523 [email protected]

Dansereau A. Air Canada Air CanadaCentre 054, PO9000

Saint-Laurent Quebec H4Y 1C2 (514) 422-6736 (514) 422-5374

Davis Max Royal Aus-tralian AirForce, AircraftStructural In-tegrity Branch

ASI-SRS-LSA,501 Wing,RAAFAmberley

Amberley Australia 07 5461-3086 07 5461 3260 [email protected]

Del Grande Nancy LawrenceLivermoreNational Lab.

P.O. Box 808,L-333

Livermore CA 94550 (510) 422-1010 (510) 422-3834

Djordjevic B. Boro CNDE, JohnsHopkinsUniversity

102 MarylandHall, 3400 N.Charles St.

Baltimore MD 21218 (410) 516-5215 (410) 516-5293

Dolan Kenneth LawrenceLivermore Na-

P.O. Box 808,L-333

Livermore CA 94551 (510) 422-7971 (510) 422-3834 dolan2.llnl.gov



Last Name First Name Name Address City State/Prov. Zip Code Number Number Addressional Lab.

Dunn Darrell SouthwestResearchInstitute

6220 CulebraRd

San Antonio TX 78238-5166 (210) 522-6090 (210) 522-5184

Finley Cindy UTEXScientificInstruments

2319 DunwinDr, Unit 8

Mississauga Ontario L5L 1A3 (905) 828-1313 (905) 828-0360 [email protected]

Fisher Jay SouthwestResearchInstitute

6220 CulebraRd

San Antonio TX 78228-0510 (210) 522-2028 (210) 684-4822 [email protected]

Forney Don UniversalTechnologyCorporation

4031 ColonelGlenn Highway

Dayton OH 45431-1600 (513) 426-8530 (513) 426-7753 [email protected]

Foster Donald LawrenceBerkeleyNational Lab.

One CyclotronRoad, MS:44B,University ofCalifornia

Berkeley CA 94720 (510) 486-6175 (510) 486-7678 [email protected]

Frances-cone

Orv Quality En-gineering TestEstablishment


French Carl Boeing 2601 LibertyParkway

Midwest City OK 73110 (405) 739-1410 (405) 739-1416

Furmanski Donald SEMCOR 815 E Gate Dr Mt Laurel NJ 08054-1240 (609) 234-6700 (609) 234-7646 [email protected]

Gergar Richard SEMCOR 65 W St RdC-100

Warminster PA 18974 (215) 674-0200 (215) 443-0474 [email protected]

Gould Ron NRC Canada Montreal Rd,Bldg M-3

Ottawa Ontario K1A 0R6 (613) 993-9133 (613) 998-8609 [email protected]

Green Robert CNDE, JohnsHopkinsUniversity

102 MarylandHall, 3400 N.Charles St.

Baltimore MD 21218 (410) 516-6115 (410) 516-5293 [email protected] U




Griffiths Brian Air Canada Air CanadaCentre 015, PO9000

Saint-Laurent Quebec H4Y 1C2 (514) 422-7219 (514) 422-7820

Hay D. Robert Tektrend 2113A StRegis Blvd,Dollard

Montreal Quebec H9B 2M9 (514) 421-1417 (514) 421-1487

Hinders Mark College of Wil-liam and Mary

PO Box 8795 Williamsburg VA 23187-8795 (757) 221-1519 (757) 221-2050 [email protected]

Hinton Bruce DSTO Aus-tralia, Aeronau-tical and Mari-time ResearchLaboratory

506 LorimerStreet,FishermensBend,Melbourne

Victoria Australia 3207 03 9626 7535 03 9626 7096 [email protected] v.au

Hinton Yolanda US ArmyResearch Lab.

AMSRL-VS-S(MS 231),NASA LaRC

Hampton VA 23681-0001 (757) 864-4950 (757) 864-4914 y.l.hinton@larc .nasa.gov

Hockings Colin Qantas M271G Mascot2020

Mascot Australia 2020 61 2 691 7402 61 2 691 8150

Howard A. Quincy Boeing PO Box 3707,MS 9U-EA

Seattle WA 98124-2207 (425) 234-8180 (425) 234-8501 [email protected]

Hull Amy Argonne Na-tional Lab.

9700 S. CassAvenue,ET/212

Argonne IL 60439-4838 (630) 252-6631 (630) 252-3604 [email protected]

Kenny Paul JacksonvilleNADEP

Code 341 Jacksonville FL 32212-0016 (904) 772-4520

Lai Ken DSTO, Aus-tralia, Aeronau-tical and Mari-time ResearchLaboratory

506 LorimerStreet, Fishe-rmens Bend

Victoria Australia 3001 03 9626 7408 03 9626 7096

Lake Richard C.W. Pope &AssociatesPTY Ltd.

24 CallisternonClose

Warabrook Australia 2304 612 49672788 612 49601030




Lamb Stephen DSTOAustralia

P.O. Box 4331Melbourne

Victoria Australia 3001 03 61 3 96267525

03 61 3 96267089

[email protected]

Lepine Brian NationalDefence Canada

CRAD/AVRS3-3 NationalDefence HQ

Ottawa Ontario K1A 0K2 (613) 991-5963 (613) 993-4095 [email protected]

Mal Ajit UCLA 420 WestwoodPlaza, Box951597

Los Angeles CA 90095-1597 (310) 825-5481 (310) 206-4830 [email protected]

May Robin ETRS 75 AshleyStreet, WestFootscray

Victoria Australia 3012 03 9434 4783 03 9689 6923

McAdam Grant DSTO Aus-tralia, ShipStructures andMaterialsDivision

P.O. Box4331,Melbourne

Victoria Australia 3001 03 9626 7398 03 9626 7096 [email protected]. gove.au

Miller W.J. (Bill) TransportCanada

Place de Ville330 Sparks St,2nd Fl

Ottawa Ontario K1A 0N8 (613) 952-4388 (613) 996-9178 [email protected]

Monchalin Jean-Pierre NRC Canada 75 de Mortagne Boucherville Quebec J4B 6Y4 (514) 641-5116 (514) 641-5106 [email protected]

Moore Barbara U.S. ArmyPacific, ATTN:ASPA

Bldg. T-115,Room 118

Ft. Shafter HI 96858-5100 (808) 438-1480 (808)438-6242 [email protected]

Neiser Donald U.S. Air ForceOklahoma CityALC

OC-ALC/LACRA, 3001Staff Dr., Ste2AC489 D

Tinker AFB OK 73145-3019 (405) 736-3834 (405) 736-5604




Nihei Kurt LawrenceBerkeleyNational Lab.

One CyclotronRoad, MS: 90-1116, Building51N, Room 2,University ofCA

Berkeley CA 94720 (510) 486-5349 (510) 486-5686 [email protected]

Prosser G. Bryan Marine CorpsSystemsCommand

Code PSE-P Quantico VA 22134-5080 (703) 784-4550 (703) 784-3432 [email protected]

Rennell Robert ARINC 6205 S. SoonerRd

Oklahoma City OK 73135 (405) 739-0939 (405) 739-0003 rrennell@arinc. com

Robertson MAJ David AF CorrosionProgram Office

WL/MLS-OL,420 2nd St,Suite 100

Robins AFB GA 31098-1640 (912) 926-3284 (912) 926-6619 darobert@wrdis s1.robins.af.mil

Roth Martin Quality Engi-neering TestEstablishment


Rudd William Mid AtlanticRegional Cali-bration andMaterials TestLab

Materials Eval-uation Section,Code 134.22,9349 FourthAvenue

Norfolk VA 23511-2116 (757) 445-8822 (757) 444-6229

Ruedisueli Robert University ofWashington

APL, 1013 NE40th St

Seattle WA 98105-6698 (206) 543-9825 (206) 543-6785 [email protected]

Sakai Jeff Naval AviationSystemsCommand

Building 469,Code 43400,NAS, NorthIsland

San Diego CA 92135-5112 (619) 545-9756 (619) 545-7810

Scala Christine DSTOAustralia

GPO Box 4331Melbourne

Victoria Australia 3001 christine.scala @dsto.defence. gov.au

corrosion detection technologies - acqweb - offices of the under

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