Technical Corrosion Collaboration (TCC)

Research Projects at the University of Akron 2010-2013

Fiscal Year 2013: United States Air Force Academy Project Principal Investigator Research and Development Transfer of Corrosion Prevention and Control Technologies

S. Lousher

Influence of Ductile Damage on Stress Corrosion Cracking of Commercially Pure Titanium

X. Gao

Effects of Topography, Microstructure, and Surface Chemistry on Stress Corrosion Cracking in 300M, 17-4PH, and AA7075-T6 Materials

G. Doll

Damage Evolution of DEFT Coating/7075 T6 Alloy-System Under Stress Conditions Based on Advanced Electrochemical Techniques and Reliability Analysis

H. Castaneda

Research and Development for the Corrosion Damage and Remaining Strength Predictions of Steel Plates, Stiffeners And Stiffened Panels

A. Patnaik

Microbiologically Influenced Corrosion of Stainless Steel 304L in Water Systems

L. Ju

A Model of Damage Evolution During Galvanically Accelerated Corrosion at Lap Joints

S. Lillard, G. Young

Flexible Epoxide Primers with Improved Undercut Performance

M. Soucek

Fiscal Year 2012: Army Corps of Engineers Research Laboratory Project Principal Investigator

The Integration of Theoretical and Experimental Corrosion Assessment Tools to Monitor and Manage Coating/Substrate Integrity

H. Castaneda

Microbiologically Influenced Corrosion Bi-min Newby Localized corrosion and stress corrosion cracking of magnesium and magnesium alloys

H. Cong

Real time corrosion monitoring of microbially induced corrosion in water-cooling systems

C. Monty

Real-Time In Situ X-ray Tomography Imaging of Crevice Corrosion

S. Lillard

Evaluation of Galvanic Corrosion S. Lillard Development of a Steel Reinforced Concrete Corrosion Monitoring and Management System

A. Patnaik

Self-Stratifying Corrosion Resistant Coatings M. Soucek High Performance Alkyd Coatings M. Soucek Model for Crevice Corrosion Damage Evolution G. Young

*Click on Project title or name of PI to learn more

Technical Corrosion Collaboration (TCC)

Fiscal Year 2011: Army Corps of Engineers Research Laboratory Project Research Team

Role of Non-Uniform Corrosion Prod Growth on Steel Degradation

A. Patnaik

Risk Assessment for Steel Structures G. Young Evaluation of Galvanic Corrosion S. Lillard Damage Evolution Modeling & Computational Simulation G. Young Unification of Coating Damage Measurements H. Castaneda Investigation of Organic Coating Interaction with Metals and Alloys

M. Soucek

The Effects of Nanomaterials on Corrosion Resistant Coatings

M. Soucek

Rapid Assessment of Coatings H. Castaneda Initial Stages of Biofilm Formation & Microbiology Influenced

Bi-min Newby

Risk Management of MIC J. Senko Induced Current Corrosion S. Lillard

Fiscal Year 2010: United States Air Force Academy Project Research Team Corrosion Management in System Health Monitoring J. Payer

Crevice Corrosion Damage Evolution G. Young, J. Payer

Contrast Corrosion Damage Evolution in Laboratory Tests and Atmospheric Exposures

J. Payer

Initial Stages of Biofilm Formation and Microbiologically Bi-min Newby

Electromagnetic Radiation Effects on Corrosion/Induced Corrosion

J. Payer, N. Ida

Investigation of Organic Coating Interaction with Non-Standard Metal or Alloys

Bi-min Newby

Coating-Metal Interaction & Strippable Primer/ Enzyme Strippable Primer

M. Soucek

Friction Stir Welding for Assembly of Aerostructures A. Patnaik

*Click on Project title or name of PI to learn more

Project Title: Research and Development Transfer of Corrosion Prevention and Control Technologies

Principle Investigator: S. Fawaz

Work Statement: The proposed plan for developing and integrating environmental-fatigue research results into the DoD airframe fatigue management framework involves several steps. The first is developing scientific understanding for a relevant material under loading and environmental conditions pertinent to real world applications. Second, to incorporate this understanding into engineering methods that are rigorous, simple to implement, and are validated in laboratory conditions representative of realistic operation. Lastly, to support/collaborate with DoD labs and small businesses who interface with airframe structural managers to perform field level validation and integrate these methods into an airframe prognosis protocol. The first two steps are addressed in the scientific research on-going in the TCC program; it is the last step that is the focus of the proposed work. The result will be an additional engineering tool for the airframe structural prognosis community which can be applied to targeted environment-induced issues to help maintain fleet safety while reducing costly over-conservatism.

Environment affects fatigue behavior in two important ways (1) pre-existing corrosion damage enhances the local stress/strain state which accelerates crack formation and can influence local growth, and (2) the interaction between the material at the crack tip and the surrounding environment concurrent with loading significantly affects crack progression. Currently the DoD Aircraft Structural Integrity Program (ASIP) community fails to model either both phenomenon. Any corrosion damage is immediately removed (the “find and fix” approach). Additionally, both the USN safe-life and the USAF damage tolerant fatigue management approaches use material properties gathered in moist laboratory air (RH ≈ 20-70%) for structural life predictions. For an airframe relevant Al alloy (7075-T651), recent OSD funded research at the University of Virginia (UVa) has greatly enhanced the scientific understanding of crack progression from corrosion damage and validated a fracture mechanics approach to predicting remaining fatigue life from a corroded surface. Furthermore, a large beneficial effect of typical high-altitude/low- temperature airframe loading conditions on fatigue life has been demonstrated. Whether it is corrosion fatigue modeling to enable continued flight of a corroded component until more skilled repair/replacement occurs in alignment with a depot cycle or decreasing the inspection burden for components that are primarily loaded in high-altitude/low-temperature environments; both topics could significantly impact structural integrity. Currently, this new capability has not been implemented in a robust, accessible modeling framework and thus is not accessible to the structural integrity managers.

The technical inputs for empirical modeling of crack formation and fracture mechanics modeling of crack progression from pre-existing damage in 7075-T651 have been established and the modeling procedure has been validated via laboratory experiments. Due to the technical maturity of this topic the remaining challenges are to incorporate the technical knowledge into a life prediction tool (AFGROW), inform the structural management community, interface with CAStLE/DoD laboratories to identify possible targeted applications, and perform field level validation of this methodology. For example, factors governing crack formation from corrosion

damage were identified and a methodology developed that accurately predicts formation life, however incorporation of these ideas into a readily available prognosis tool has yet to be realized.

The primary engineering hurdles remaining are gathering a coupled load-environment spectrum and developing an algorithm that incorporates environment specific growth rates into a fracture mechanics framework. To address the former CAStLE is analyzing flight data from an USAF A-10, the latter will be addressed in this effort.

For both corrosion-fatigue and temperature dependent fatigue, CAStLE will serve as the primary conduit to military application. The UA-CAStLE-UVa collaboration offers an ideal university and government partnership. Where the UA/UVa provides the necessary scientific basis, CAStLE uses its strong ties to the

structural fatigue community to transition the new technology. For both topics the LEFM software AFGROW is capable of evaluating the effectiveness of these modeling techniques given the appropriate operational inputs.

Task 1: Development of Time/Cycle Damage Accumulation Framework

Modeling damage accumulation in the time or cycle domains is complicated individually; thus, coupling of the damage accumulation mechanisms only increases the complexity of the modeling task. The damage accumulation framework provides the process/requirements flow for each step of the analysis. For the corrosion, fatigue, and fracture models considered, the required data input, assumptions, algorithm, interfaces, and output will be defined. A gap analysis will be conducted to determine the completeness of the input data and algorithms. Corrosion fatigue interface relationships will be defined as required. It should be anticipated that all modeling requirements cannot be met with the state-of-the-art; thus, capability gaps will also be identified and a roadmap for filling the gaps will be developed where known challenges and constraints are identified.

Task 2: Evaluation of Corrosion Models

Of the 17 corrosion mechanisms, service history has shown that several corrosion mechanisms are most important in DoD weapon systems. Specifically corrosion pitting, crevice corrosion, and exfoliation corrosion cause a large inspection and maintenance burden for DoD aviation assets and will be evaluated for incorporation in the structural integrity framework. Pitting, crevice, and exfoliation corrosion models are available from the University of Akron (Young), University of Virginia (Kelly), and Ohio State University (Frankel), respectively. A brief description of each model is given below.

Task 3: Integration of Corrosion Models in Structural Integrity Framework

The fundamental goal of the corrosion modeling described in Task 2 above is to provide inputs to fracture mechanics models that determine structural integrity. The algorithms described are meant to be of use to ASIP managers in making the decision with regards to what to do with an NDI assessment of corrosion. AFGROW is a fracture mechanics based Damage Tolerance Analysis (DTA) framework that allows users to analyze crack initiation, fatigue crack growth, and fracture to predict the life of metallic structures. This program will add consideration of environmental effects to the AFGROW toolset. AFGROW is mainly used for aerospace applications; however, it can be applied to any type of metallic structure that experiences fatigue cracking. The classic stress intensity factor library provides solutions for over 30 different crack geometries (including axial, bending and bearing loading for many cases). In addition, an advanced, multiple crack capability allows AFGROW to analyze two independent cracks in a plate (including hole effects), non-symmetric corner cracked holes, and a continuing damage solution. Finite Element (FE) based solutions are available for two, non-symmetric corner cracks at holes as well as cracks growing toward holes. This capability allows AFGROW to handle cases with more than one crack growing from a row of fastener holes commonly found in aircraft structure. AFGROW implements five different material models (Forman Equation, Walker Equation, Tabular lookup, Harter-T Method and NASGRO Equation) to determine crack growth per applied loading cycle. Other AFGROW user options include five load interaction (retardation) models (Closure, FASTRAN, Hsu, Wheeler, and Generalized Willenborg), and a strain-life based fatigue crack initiation model. AFGROW also includes useful options such as: user-defined stress intensity solutions, user-defined beta modification factors (ability to estimate stress intensity factors for cases, which may not be an exact match for one of the stress intensity solutions in the AFGROW library), and a residual stress analysis capability. AFGROW also includes a plug-in stress intensity solution interface that allows AFGROW users to develop additional stress intensity factor (K) solutions representative of corrosion damage although K solution development is not within the scope of this effort. In consideration of the above, AFGROW is the logical choice for including environmental effects in structural integrity fleet management decision making.

Task 4: Validation of Model Integration

Controlled laboratory experiments will be conducted to produce a set of data to validate the specific corrosion fatigue modeling integration developed. Care will be taken to produce data that uses the test condition(s) (corrosion mechanism selected from Task 1 and 2) that are being modeled in order to reduce the uncertainty in the validation. The gold standard for model validation is to use actual in-service damage data; however, such a validation effort is not within the scope of this program.

Product (deliverables):

The proposed research will provide the integration of select corrosion fatigue damage mechanisms into the AFGROW life prediction tool which enable next generation simulation of environmentally assisted cracking in specific DoD components. This tool will identify the risk of such cracking as a function of a range of important variables, and suggests paths to optimizing inspection intervals, component readiness, and risk. The following will be delivered under this effort.

• Quarterly quad charts

• Conference papers and archival journal papers if applicable

• Final report

• Time/cycle damage accumulation AFGROW modules

Relevance and Cost of Corrosion Relationship: The contribution of a moist environment to fatigue damage in aluminum alloys is substantial and difficult to model in currently deployed mechanics-based structural life prediction codes. Substantial work has been performed to incorporate the effects of mechanical loading spectrum into prognosis modeling of fatigue damage; however, similar efforts have not been put forth to understand the strong influence of environmental spectrum. Fatigue behavior is governed by both mechanical (stress intensity range, ΔK) and chemical driving forces; as such the loading environment significantly affects the fatigue life of aluminum components. Specifically, loading in a moist-air environment produces atomic hydrogen (H) that enters the material at the crack tip and enhances damage by one or more unique mechanisms. Airframe engineers employ either a fracture mechanics (USAF) or safe-life approach (USN) to manage the effect of fatigue on structural integrity. Unfortunately, the environmental effects are typically not considered; thus, threshold and recurring inspection intervals occur later in life and component end of life is over- predicted which is non-conservative in terms of flight safety.

Through this effort, the AFGROW life prediction tool will be modified to analyze environment- spectrum interaction for which a proper characterization and understanding is paramount for appropriate structural integrity estimates and fleet management decision making.

Project Title: Influence of Ductile Damage on Stress Corrosion Cracking of Commercially Pure Titanium

Principle Investigator: X. Gao and S. Graham

Work Statement: One method the DoD uses to attach tubes into the tube-sheet of a heat exchanger is hydro- forming. This process results in localized shear damage in the tubes, which may influence the propensity for stress corrosion cracking (SCC) during the life of the heat exchanger. Cracking could lead to cross-contamination of the working fluids and a loss of efficiency of the heat exchanger. The objective of the proposed work is to provide predictive capability for stress corrosion cracking to assist in the decision to monitor, repair, or plug heat exchanger tubes with known or suspected damage. Future efforts will extend the theoretical, experimental and numerical framework and models developed in this study to other materials of DoD’s interests and other process besides hydro-forming. This will be a joint collaboration between the University of Akron, the United States Naval Academy, and the Naval Research Laboratory, where a blend of experimental testing, theoretical modeling and numerical simulation work will be conducted. The tools developed in this project will lead to better designs and manufacturing processes and also for improved structural analysis and damage tolerance predictions. Task 1 – Utilizing Available Constitutive and Damage Models to Study the Hydro-Forming Process As a first step, we would like to examine the applicability of the currently available constitutive and ductile damage models and identify needs for further model development. We will utilize the available constitutive and damage models to investigate the hydro-forming process used to “lock” heat exchanger tubes into a tube-sheet. We will conduct tensile tests to obtain the stress- strain response of the material, develop an accurate tube forming experiment, section and take fractographs of the area where damage occurs, and conduct finite element simulation of the hydro-forming process using available constitutive and damage models. This will allow us to characterize the limitations of current models in predicting plastic deformation and damage initiation and propagation during the hydro-forming process. The work to be conducted can be summarized as • Task 1.1. Conduct tensile tests• Task 1.2. Design and conduct tube forming experiment• Task 1.3. Perform fractography and microstructure analysis• Task 1.4. Perform finite element analysis of the tube forming experiment using available constitutive and

ductile damage models • Task 1.5. Summarize analysis results and identify needs for further model development Task 2 – Developing

a Constitutive Model to Capture the Plasticity Behavior of CP Titanium and a Ductile Damage Model Based on Material Failure Mechanism The most popular constitutive model for metal plasticity is the J2 flow theory. This theory describes an isotropic plastic response and assumes hydrostatic stress as well as the third invariant of the stress deviator has no effect on plastic yielding and the flow stress. However, experiments have shown that the plastic behavior of CP titanium is anisotropic and exhibits tension/compression asymmetry. As for ductile fracture, the mechanism has been attributed to void nucleation, growth and coalescence. The most widely used micromechanics model for predicting ductile failure is the Gurson model with modifications by Tvergaard and Needleman. Despite its apparent success, this model suffers from several significant limitations. The most important drawback is that the model is not able to capture localization and fracture for low stress triaxiality, shear dominated deformations, since it does not predict void growth and damage evolution under shear loading. Therefore, in this study we will develop a constitutive model that captures the complex plasticity behavior of CP titanium and a ductile damage model that captures material failure under shear-dominated conditions. We will conduct experiments to assess the anisotropy and tension/compression asymmetry of the plastic response of CP titanium, develop a plasticity model that captures these behaviors, extend the Gurson-type void growth model to include shear induced damage and Lode effect, couple the plasticity and damage models and implement it into a finite element software, calibrate model parameters, and simulate the hydro-forming process to validate the numerical model. The developed model will be able to quantify damage accumulation and predict crack initiation and propagation during the hydro- forming process. This will lead to an improved predictive capability for environmentally-

assisted cracking over the life of the heat exchanger. It will also result in recommended changes to the fabrication process to avoid the formation of cracks during tube insertion. The work to be conducted can be summarized as

• Task 2.1. Conduct tension and compression tests in different orientations • Task 2.2. Develop a constitutive model that captures the anisotropy and tension/compression asymmetry of

the plastic response of CP titanium • Task 2.3. Conduct tests to characterize critical damage levels corresponding to fracture for different stress

states • Task 2.4. Extend the Gurson-type void growth model to include shear induced damage and Lode effect • Task 2.5. Implement the plasticity and ductile damage models into a finite element software, ABAQUS and

calibrate model parameters using experimental data • Task 2.6. Simulate the tube forming experiment using the developed models and assess model predictions • Task 2.7. Correlate damage predictions with SCC behavior from Task 3 tests Task 3 – Characterizing

Influence of Damage on SCC and Student Training This project will be a joint effort between Prof. Stephen Graham at the US Naval Academy and Prof. Xiaosheng Gao at the University of Akron. Dr. Erik Knudsen at the Naval Research Laboratory will also actively participate in this research. An important task of the project is to educate and train students and get them involved in this research. At UA, one graduate student and one undergraduate student will participate in this project. At USNA, the project will involve one or more undergraduate students conducting stress corrosion cracking tests on CP-Titanium tubes with varying amounts of damage to characterize the influence of damage on the time to initiate, and the subsequent rate of stress corrosion cracking. These tests will be conducted as Independent Research projects by 1/C (senior) midshipmen. In addition, students at University of Akron and Naval Academy may spend time at Naval Research Laboratory with Dr. Erik Knudsen to conduct stress corrosion cracking research. All these training efforts will teach our future engineers, scientists and naval officers about potential corrosion-assisted cracking mechanisms so that they have a better understanding of civilian/military systems and can make better-informed decisions.

Product (deliverables): The quarterly quad charts, final report, and additional publications, documents and data will be submitted through the Engineering Resource Data Management (ERDM) online system. A list of deliverables are summarized as follows 1) Quarterly quad charts summarizing research progress. 2) A final Report containing detailed descriptions of the plasticity and damage models, experiments and experimental data, model calibration process, simulation of the hydro- forming process, suggested guidelines for the manufacturing process of the concerned heat exchangers based on the analysis results, discussion of the connection between damage and SCC, and plans to extend the developed models to other materials and processes. 3) A user subroutine implementing models developed in this study into a general purpose finite element software, ABAQUS. 4) Transfer of knowledge to DOD collaborators to assist in their development of algorithms and software tools. 5) Report(s) from Independent Research projects by one or more undergraduate students at the United States Naval Academy. 6) Papers, articles and dissertations resulting from the project. 7) Experimental data and microscopy images generated in this research. 8) Presentations at annual DOD Corrosion Conference and TCC review meetings. Relevance and Cost of Corrosion Relationship: Formation of through-wall cracks in heat exchanger tubes results in cross-contamination of the working fluids and a loss of efficiency. Contamination is a particular concern when one of the fluids is hazardous, as can occur in nuclear power applications. Therefore, when part-through cracks are detected in heat exchanger tubes, a decision must be made to either periodically inspect the tube, repair it, or plug it. When cracks grow through-wall, only the latter two options are available. Plugging of tubes results in a loss of cooling capacity of the heat exchanger, which then affects the operation of the entire

system it is a part of. Therefore, having better predictive capability for stress-corrosion cracking would help in making more informed decisions on inspection schedules and when to plug tubes.

Project Title: Effects of Topography, Microstructure, and Surface Chemistry on Stress Corrosion Cracking in 300M, 17-4PH, and AA7075-T6 Materials Principle Investigator: G. Doll Work Statement: Most experiments shall be carried out in the Timken Engineered Surfaces Laboratories (TESL) and the National Center for Education and Research on Corrosion and Materials Performance (NCERCAMP), which are collocated in the Akron Engineering Research Center at the University of Akron. Microstructural investigations shall be performed at the Swagelok Center for Surface Analysis of Materials (SCSAM) at Case Western Reserve University through the auspices of MatNet, the Ohio Materials Network. Test specimens shall be fabricated from 300M, 17-4PH, and AA7075-T6 materials, and heat- treated or otherwise processed according to standards for particular applications. The topographies and morphologies of the test specimen surfaces shall be characterized within TESL by a Zygo 7300 3D optical interferometer and a JEOL 5600 SEM. Corrosion resistance of test specimens shall be evaluated through electrochemical impedance spectroscopy (EIS) and ASTM B-117 salt spray testing at NCERCAMP. Slow strain rate tensile testing shall be carried out at per ASTM G129 at a strain rate of 5 × 10−7/s in air and in 3.5    wt. % NaCl as reference and corrosive environments, respectively. Microstructural measurements (TEM) shall be performed in a FEI Tecnai F30 on sections obtained from pristine and tested specimens using an FEI Nova Nanolab 200 Field Emission Scanning Electron Microscope with Focused Ion Beam, EDS, and EBSD capabilities. These measurements should be especially informative in terms of correlating microstructural information such as grain size, grain orientations, inclusions, grain boundaries, and crystallinity with H-assisted crack propagation and general fracture mechanics characteristics. Friction and wear testing, and all surface treatments shall be conducted on existing assets within TESL. • 1.1 Baseline Testing and Characterization: EIS and SCC testing, topographical and structural

characterizations of test materials. • 1.2 Development of Mikronite Process: Topography and compressive stress characterizations; EIS and SCC

testing. • 1.3 Development of Grain Boundary Engineered ZnNi: Bipolar pulsed deposition, coating characterizations,

EIS and SCC testing. • 1.4 Development of EAP-Diamondoid: Functionalizaton procedures, bipolar pulsed deposition, EIS and SCC

testing, material characterizations. • 1.5 Development of FGM Coatings and Sealant: Coating characterizations, sealant development, EIS and

SCC testing. • 1.6 Evaluation of Test Results and Recommendations Product (deliverables): Deliverables of this project will include, but will not be limited to the following: • Quarterly Quad Charts reporting the progress made against the research schedule shown in Table 1. • Final Report • Presentations and Publications: Due to the novelty of the technologies being developed and explored, several

manuscripts will be submitted for publication, and presentations will be given at conferences and meetings.

• Graduate Student and Postdoctoral Fellow with expertise in new methodologies to mitigate stress corrosion cracking in 300M, 17-4PH, and AA7075-T6 structural materials through the combination of a novel high-energy surface finishing process that removes surface defects and imparts compressive stresses, and new coatings specifically engineered for wear and corrosion resistance.

• Knowledge Transfer on how the interactions of the metrological, microstructural, and compositional properties of surfaces affect stress corrosion cracking in 300M, 17- 4PH, and AA7075-T6.

• Participation in the Annual DOD Corrosion Conference and TCC Meetings Relevance and Cost of Corrosion Relationship: This research topic is relevant to work being performed by the Dr. E. U. Lee and colleagues at the Naval Air Warfare Center Aircraft Div., Patuxent River through their affiliation with the Joint Cadmium Alternatives Team (JCAT). In one of their recent studies [18], Cd, Zn-6Ni

and Zn-13Ni were electrocoated on 4340 steel specimens, and Al coatings were applied by both ion vapor deposition (IVD) and electroplating. Their study investigated the relative ability of these coatings to protect the substrate steel from corrosion fatigue and stress corrosion cracking. Our proposed research will also investigate the Zn-Ni materials, but we will be using the process of grain boundary engineering to improve properties and performance of those materials. Mr. Scott Grendahl, the Principal Investigator for SERDP WP-2152, is leading a project aimed at identifying the most viable and reliable test geometry and utilize it to evaluate the most prospective environmentally friendly maintenance chemicals and cadmium alternative coatings 28 that have had their use limited by the perceived risk of hydrogen embrittlement [19]. Our proposed work will utilize the test geometries identified in WP-2152 to evaluate the surface treatments developed in this proposal. The U.S. Army Tank Automotive Research, Development and Engineering Center’s (TARDEC’s) Metallurgical and Failure Analysis Laboratory specializes in providing material evaluation and identification, microstructural evaluation, hardness testing and fracture analysis to assess component failures on all vehicle and weapons systems. This project will involve Mr. Demetrios A. Tzelepis, Materials Engineer at TARDEC in the materials analysis of the test specimens.

Project Title: Damage Evolution of DEFT Coating/7075 T6 Alloy-System Under Stress Conditions Based on Advanced Electrochemical Techniques and Reliability Analysis

Principle Investigator: H. Castaneda-Lopez

Work Statement: The proposed work includes four phases. Phase I (15 months) will focus on the development of the transport mechanisms that occur when an intact and defect coating exists. This will involve the definition of the damage evolution under stress-free conditions, and continuous corrosion environment, which will be used as the prototype model system for the experimental setup. Phase II (15 months) will develop the coating layered system using the theoretical modeling of the prototype system, considering constant load and corrosive environmental conditions. Phase III (12 months) will develop semi-empirical functional relationships based on experimental parameters for the coating layered system under cyclic stress (fatigue) in corrosive environmental conditions. Phase IV (27 months) will focus on probabilistic performance evaluation of the coating/substrate system based on the results obtained from Phase I, II, and III.

Phase I: Elucidation, quantification, and characterization of transport and interfacial mechanisms for damage Task 1 Baseline testing and mechanism characterization in physical prototype models Task 1.1 Development and characterization of transport mechanisms: water infiltration, mass transfer, sorption, and charge transfer in the substrate/layer(s)/electrolyte prototype systems Task 1.2 Functional relationships for transport mechanism parameters associated with coating layers (thickness and morphology), electrolyte properties (pH and ionic species) for systems under stress-free conditions Task 1.3 Development of heterogeneous transmission line modeling (TLM) Phase II: Comprehensive characterizations of the damage evolution mechanisms of the multilayer-interface configuration under constant stress Using the understanding of Phase I, new testing and theoretical analyses will be conducted to develop the transport mechanisms for constant deformation samples under constant stress. Phase 2 will consist of one overall task with two sub-tasks and last 15 months. Task 2 Characterization of transport and interfacial mechanisms for damage evolution under different constant stress conditions Task 2.1 Experimental characterizations and quantification of damage evolution of aluminum/coating layering interface for prototypes under constant stress conditions Task 2.2 Mathematical modeling in multilayer configuration for prototype under constant stress conditions Phase III: Comprehensive characterizations of the damage evolution mechanisms of the multilayer-interface configuration under cyclic loading (fatigue corrosion) Task 3 Experimental characterizations and quantification of damage evolution of aluminum layering interface under cyclic stress (fatigue corrosion) Phase IV: Performance evaluation of coating system considering uncertainties Task 4.1 Development of probabilistic capacity and demand models to capture the transport mechanisms leading to corrosion Task 4.2 Conducting reliability analysis Product (deliverables):

• A basis for novel real-time monitoring of degradation/performance of the coating/substrate system to assist in establishing guidelines for assessing non- hexavalent-chromium/substrate system reliability under different stress conditions

• A basis to develop coating maintenance using “aesthetics-driven” vs. coating integrity algorithm • A framework to elucidate, quantify and characterize mechanisms of coating removal and residual effects on

the substrate under different stress conditions • The publication of findings in technical quarterly and final report • The publication of 1 conference paper and 1 journal article per year • Presentations for annual DoD corrosion conference and TCC meetings • A Ph.D. student who will work in a highly interdisciplinary area

• Quarterly Quads charts Relevance and Cost of Corrosion Relationship: Relevance for this research includes more reliable evaluation of coating systems service, and enhanced performance assessment and life prediction. Also, the goal of the proposed work is to contribute methods or technologies used as monitoring or risk management tools of DoD assets. The definition and quantitative descriptions of damage evolution (shape and depth of corrosion) and the reliability models with different failure modes will be used for corrosion assessment, structural analysis, and risk management for maintenance and repairing programs. The impact of corrosion on the safety, affordability, and sustainability of US Air Force assets is a long-standing concern within the Department of Defense. While the absolute magnitude of the corrosion problem might not be accurately quantified, recent studies have shown significant progress on estimating corrosion-related costs and evaluating availability impacts. In order to maintain a desired level of US Air Force assets exposed to corrosion, there is a need to further understand the performance of the corrosion-impacted coating system used in the US Air Force.

Project Title: Research and Development for the Corrosion Damage and Remaining Strength Predictions of Steel Plates, Stiffeners and Stiffened Panels Principle Investigator: A. Patnaik Work Statement: The methodology developed in our currently ongoing TCC project demonstrated how corrosion will affect structural members as they interact with each other in a framed system. The ultimate goal in the assessment of remaining life is to relate thickness loss in the system to the performance of individual structural elements in order to better predict the reliability of the members and their remaining life span. In the proposed project, this methodology will be applied to the structural steel configurations that are of importance in naval applications. Corrosion defects in a vessel3 are mainly as shown in Figure 1: (i) general corrosion – uniform net section loss (ii) pitting corrosion (iii) edge corrosion and (iv) grooving corrosion. The deficiencies due to general corrosion are addressed by thickness additions at the time of initial design. However, other forms of corrosion become equally important in vessel structural components. This proposed project will address the effects of these four forms of corrosion on the performance of structural elements. Our current work (uniform corrosion) and that described by Needham (pitting), e.g. see the Section on DoD Collaboration below, focused on general corrosion (i). A key objective of the proposed project is to extend the work to other forms of corrosion (ii, iii, and iv). Another extension of the current work is also to develop treatments for incorporating corrosion rates into the methodology. When corrosion rates are incorporated into the methodology, the treatment not only assesses current structural strength and remaining life, but also treats damage evolution and life prediction. The goal is to direct the proposed work to interface with the Navy efforts, so the advances are more readily incorporated, and our work would facilitate in moving toward field implementation. Typical structural components of naval vessels are decks, sides (shell or skin), frames, bulkheads, overheads, and compartments (internal structure with stringers, web frames, girders, etc.). The common structural elements of these components are plates that are normally stiffened with different types of stiffeners. The research work done in our current TCC project mainly addressed frame elements. The elements of building frames are generally made from hot-rolled thick walled sections that are mostly capable of developing a plastic state of behavior at failure. However, the structural elements in a vessel are predominantly plate elements with stiffeners resulting in built-up configurations. The failure mode of plate elements is generally by buckling of the elements. Condition assessment and rating of plate elements in ships is normally done with ultrasonic thickness measurements (UTM). These measurements provide a basis for the determination of the remaining life of the elements. The primary structural issues and failure modes in built-up stiffened panels are: • (i) Tensile or compressive yielding • (ii) Compressive buckling and instability • (iii) Fatigue and endurance limits • (iv) Brittle fracture due to crack grow from fatigue • (v) Creep • (vi) Corrosion related thickness losses The above design issues and those listed in Figure 2 will be addressed to establish a correlation between the extent and rate of the four forms of corrosion degradation with the structural performance and remaining life predictions of plates, stiffeners and stiffened panels. The interaction between these four forms of corrosion damage will also be investigated through coordinated theoretical and experimental studies.

Product (deliverables): • Compilation of a document related to analytical and experimental research, and identification of specific

research needs for naval vessels • Insight into the degradation mechanisms of steel plates, stiffeners, stiffened panels, and connections • Theoretical developments on the remaining strength and remaining life of plates, stiffeners, and stiffened

panels • Summaries of current practices to prevent, contain, manage, maintain and protect steel plates, stiffeners and

stiffened panels from corrosion problems • Technical reports/publication(s) of the findings, journal or conference papers • Additional publications, documents and data to be uploaded to ERDM as required • Training of students and “transfer of knowledge” to co-collaborators • Technical assessment of findings and recommendations for continued development • Participation in TCC meetings, annual DoD Corrosion conference, technical conferences and corrosion

forums • Quarterly quad charts and progress reports as needed • Final report Relevance and Cost of Corrosion Relationship: Corrosion of plates, stiffeners and stiffened panels, and the related connections is a problem that is very important to US Navy. Modeling from the corrosion process to the system performance has great benefits for applications both in the defense and civilian sectors. Quantitative evaluations of corrosion related deterioration of vessel structural components are required for performance assessment, design, preventive maintenance, and risk management. These issues will be addressed in the proposed project in consultation with Mr. Needham and his team.

Project Title: Microbiologically Influenced Corrosion of Stainless Steel 304L in Water Systems Principle Investigator: L. Ju Work Statement: MIC has attracted much attention [3-9]. The phenomena associated with MIC are very complex. Much of the critical knowledge is still missing, particularly in the responsible mechanisms and roles of specific microbes for initiation and subsequent evolution of corrosion. In addition, MIC is sensitive to the microbes’ interactions with environmental conditions and other non-biological factors and processes/reactions. So far MIC has been difficult to identify and mitigate [4-6]. SRB and FeOB are two important groups of aggressive iron corroders. Under anaerobic or microaerobic conditions, SRB are often associated with the hard-to-detect, and thus potentially disastrous, pitting corrosion of carbon steels. On the other hand, under aerobic and physiologically suitable acidic conditions, FeOB can significantly accelerate the iron corrosion rates. However, the effects of SRB and FeOB on stainless steel corrosion have not been well studied. In this project, we will examine the attachment and biofilm development of SRB and FeOB, separately, on stainless steel surfaces under different water flow and other environmental conditions. We will also quantify the pitting and surface corrosion rates of SRB and FeOB on stainless steel and elucidate the mechanisms and critical factors dictating the associated MIC. In particular, Desulfovibrio vulgaris and Acidithiobacillus ferrooxidans will be used as the model SRB and FeOB, respectively. Stainless steel 304L will be used as the model metal substrate. 300-series of austenitic stainless steels (SS) are most common construction metals used for storage tanks, high pressure firefighting and water transportation pipelines, and SS 304L is one of the most typical low carbon grade 300-series SS. Task Plan Summary: • Evaluate the basic interactions between a sulfate reducing bacterium (D. vulgaris) and an iron oxidizing

bacterium (A. ferrooxidans) on stainless steel 304L • Fabricate SS 304L to have three different microstructures resulting from welding • Investigate the attachment of D. vulgaris and A. ferrooxidans on SS 304L with different microstructures • Monitor the biofilm development of D. vulgaris and A. ferrooxidans on SS 304L with different

microstructures • Assess and quantify how microbial activities and metabolites of D. vulgaris and A. ferrooxidans affect

corrosion behaviors of SS 304L • Determine how the presence of bacterial biofilms may accelerate stainless steel corrosion • Elucidate corrosion mechanisms to facilitate future modeling, prediction, and mitigation of MIC corrosion on

SS 304L. Product (deliverables): • Determine bacterial attachment behaviors of two aggregative steel corroders on SS 304L • Estimate the strength of bacterial cells and biofilm of an FeOB and a SRB attached to SS 304L • Generate evidence that supports or disproves the role of microbial biofilms in accelerated SS corrosion -

whether SRB and FeOB biofilm will directly cause MIC in SS 304L • Obtain quantitative correlations of metabolite concentrations to SS 304L corrosion • Establish empirical correlations of SS 304L corrosion with the biofilm development and structure • Gain understanding of MIC mechanisms on SS, and • Provide foundation for better modeling, prediction and mitigation of MIC on SS. Programmatically, we will submit quarterly quad charts and a final report according to schedule, and will attend annual DOD Corrosion Conference and TCC meetings. The knowledge generated in the project will be further disseminated by publishing at least two refereed journal articles and making at least 4 oral and poster presentations at professional conferences. At least two graduate students and two undergraduate students will be involved in this project. They will gain research and/or laboratory experience in the corrosion field, valuable to their future professional careers and contributions.

Relevance and Cost of Corrosion Relationship: Design of this proposed study of MIC on stainless steel 304L in water systems has benefited tremendously from our communications with Mr. Norman Clayton, a materials engineer in the Corrosion and Coatings Engineering Branch at the Naval Surface Warfare Center, Carderock Division (Philadelphia, PA). Mr. Clayton has identified this as a very relevant and important topic to DOD. Our research team will visit Mr. Clayton at an early stage of the project to observe the corrosion on site and follow up with more communications. We will conduct the laboratory study under conditions closely simulating those exhibiting MIC at DOD sites. Throughout the study we will consider how to best apply the project results and findings to the DOD relevant water systems, and gather inputs from Mr. Clayton, Dr. Brenda Little, Dr. Jason Lee, and other potential DOD personnel.

Project Title: A Model of Damage Evolution During Galvanically Accelerated Corrosion at Lap Joints Principle Investigator: S. Lillard and G. Young Work Statement: Task 1 Corrosion Damage Model We will develop, formulate and validate a model of the damage evolution that results from galvanically accelerated crevice corrosion below the fastener head. Figure 1 illustrates this geometry. To accomplish this we will couple our existing crevice and galvanic corrosion models and define the computational framework necessary to model mass transport, interphase mass transfer, and chemical reactions within the bulk and within the crevice at the metal solution interface. To provide input for the model, it will be necessary to conduct experiments to determine the potentiodynamic response for materials in solutions to represent “bulk” environments (well mixed) as well as solutions to represent local changes in pH, cation concentration and anion concentration that might develop at the interface or in the crevice (i.e. representing the critical crevice solution). Our previous computational experience in corrosion simulations suggests that the model predictions are extremely sensitive to these current potential data. To benchmark our model predictions we will use data from the AFRL prototypes described below as well as data generated in our laboratories from couples of Al 7000 series alloys with fastener materials in geometries identical to those used in our modeling calculations. During these exposures current and potential distributions will be interrogated using the scanning vibrating electrode method (SVET) and the scanning reference electrode technique (SRET). Following the exposure period, damage evolution will be measured using optical profilometry, a so-called 3D microscope. Each of these experimental data sets (current, potential, damage) will be compared to the corresponding set from our model predictions as a measure of model benchmarking. Task 2 Detection Methods for Corrosion We will work with AFRL to develop a protocol for monitoring corrosion rate in the generic structural component for coating structural failure being developed in their labs. To accomplish this we would design a non-destructive electrochemical methodology for each exposure stage. For example, to detect corrosion during sample fatigue stage we would design an enclosure for the component that would contain the solution and the necessary electrodes to perform electrochemical impedance spectroscopy (EIS). EIS is a powerful non-destructive technique that can be used to monitor water uptake in organic coatings as well as pores (both macroscopic and microscopic) that develop in these coatings.[Kendig 1990] A similar method would be used to evaluate the coating after salt-fog or outdoor exposure stage. To accomplish this we will use a 60 barnacle type cell, so named because it can easily be attached and removed from flat surfaces without damage to them. The barnacle cell would contain a small amount of solution and the necessary electrodes to perform EIS as described before. Given that the scope of this task is fairly straightforward, the project would be a good candidate for the Student Intern Program described below. Task 3 Student Intern Program As part of this funding, we will establish a corrosion student intern program. This intern would likely be a UA undergraduate student that would work at AFRL during the summer and in our labs during the school year. The University of Akron has the only baccalaureate program in corrosion engineering and an intern of this type would compliment the students course work and, possibly, prepare the student for future employment at one of the DoD labs. Product (deliverables): As part of this proposal we will submit reports to DoD on a quarterly and annual basis. Quarterly reports will be in the form of Technical and Financial Progress Reports. These reports will be formatted in the appropriate DoD manner and include any online applications for status tracking. In addition to these quarterly updates, we will also submit yearly reports as well as a final report to DoD. In accordance with the solicitation, the quality assurance requirements regarding record keeping, methodology, personnel training, peer review and documentation, will be met by using existing University processes or by using the guiding documents provided by ONR, as appropriate.

Relevance and Cost of Corrosion Relationship: AFRL has recently begun developing an accelerated test protocol to simulate the combined effects of fatigue and atmospheric exposure on the structural failure of coating systems at lap joints in aircraft.[Thompson, 2012] One of the designs for a generic structural component to be used in this protocol is shown in Figure 3. In this component the structure that represents the aircraft "skin" would be made from Al 2XXX or 7XXX series alloys while the fasteners would be made from steel or possibly titanium. This component would be alternately exposed to outdoor atmosphere (or B117) and fatigue cycles to evaluate the durability of the coating system. Care will be taken so that fatigue loads will not dominate the failure process (e.g. corrosion fatigue will be avoided). In this manner the study will focus on the mechanical failure of the coating and the subsequent effects of galvanically induced corrosion. In the first stage of the program, the AFRL goal is to demonstrate that the test specimen can produce similar results as observed from actual aircrafts. The component would be evaluated by visual inspection, NDE (radiographic and ultrasonic) during the test. However, no real-time electrochemical data for the components will be collected. Instead, some specimens will be completely disassembled for metallographic evaluation after the exposure period.

Project Title: Flexible Epoxide Primers Principle Investigator: M. Soucek Work Statement: Bisphenol-type epoxides are the workhorse of primer coatings for metal substrates in general and in particular for the DOD assets. A particular problem for thermosetting BPA epoxides is cracking. The cracking leads to a defect, which quickly leads to corrosion. Cracking is caused by a number of causes depending on the DOD asset. For Aircraft, there is the pressurization depressurization cycle as well as large swings in temperature. The temperature swing can exacerbate CTE differences between the metal substrate and coating. Other DOD assets have impact issues with large swings in temperature. In summary, cracking of BPA-epoxides is quite universal. Hypothesis The cracking of the primer due to pressure-depressurization and thermal cycling can be mitigated by adding pendent aliphatic side groups on the epoxide. This will contribute to free volume, and therefore ameliorate cracking of the primer during pressurization/depressurization cycling. It is proposed that Dr. Soucek’s Group work on creating a more flexible primer without decreasing it’s corrosion performance or other pertinent coating properties. It is proposed to modify the commercially available epoxides using terminal alcohols followed by reaction with epichlorohydrin as shown in Figure 1. In this way, the crosslink density should not adversely effected (too much), yet ethyl butyl, or hexyl groups can serve as self-plasticizing pendent groups without interfering with the crosslinking reactions. Task 1: Preparation of the epoxide, Characterization of the modified epoxide Task 2: Scale-up of chemistry for testing Task 3: Form cooperative agreement with Air Force Academy/UVA for environmental evaluation of cracking behavior. Task 4: Preliminary Coating Testing, curing Optimization, Formulation with and without Pigment, hardness, DMTA, DSC, AFM, adhesion Task 5: Fracture toughness measurement Task 6: Corrosion and weathering testing: EIS Salt-spray, after topcoated deployment in Hawaii, and Weatherometer Task 7: Arrange deployment of test samples on aircraft and vehicles for evaluation Product (deliverables): -Understanding of Coating Process around Rivets and how this effects corrosion protection -Links coating cracking with corrosion related stress cracking -Provides coating solution with a more flexible primer coating to ameliorate this problem Communication -Reports to in Quad charts quarterly, and Gannt charts -Attendance and presentation at TCC meetings -Meetings with and presentations to principle collaborators at AFRL every 6 months with written reports and at NavAir and ARL at least once a year. Relevance and Cost of Corrosion Relationship: Aircraft in particular suffer from cracking of the primer around the exterior and particularly around rivets. Bisphenol-type epoxides are the workhorse of primer coatings for metal substrates in general and in particular for the DOD assets. A particular problem for thermosetting BPA epoxides is cracking. The cracking leads to a defect which quickly leads to corrosion. Cracking is caused by a number of causes depending on the DOD asset. For Aircraft, there is the pressurization depressurization cycle as well as large swings in temperature. The temperature swing can exacerbate CTE differences between the metal substrate and coating. This is especially true with areas with rivets. Other DOD assets have impact issues with large swings in temperature. In summary, cracking of BPA-epoxides is quite universal for most coated aircraft and most DOD vehicles.

Project Title: The Integration of Theoretical and Experimental Corrosion Assessment Tools to Monitor and Manage Coating/Substrate Integrity

Principle Investigator: H. Castaneda

Work Statement: Two technological challenges will be addressed in this proposed Phase I research for assessing the performance of Department of Defense (DoD) assets and estimating their reliability: (1) to characterize the damage evolution and quantify the corrosion process in organic and inorganic coatings in different substrates and environment conditions (2) to develop an algorithm based on deterministic-stochastic modeling and novel multi-scale monitoring system.

For the first challenge, we propose to develop a conceptual framework and theoretical models to characterize the critical performance/damage parameters for laboratory designed and commercial available coatings (organic/inorganic) with substrates (steel, aluminum, magnesium) that are significant to DoD. The theoretical models will correlate the critical parameters forming the interface coating/substrate with the environmental effects existed on DoD assets used in land, air, or sea applications. For the second challenge, we propose to use the integration of deterministic-stochastic damage evolution model with a multi-scale experimental approach, which includes the design of a real-time monitoring system. The damage evolution model will be used to describe the material degradation at the coating, the coating/metal interface, and the metallic substrate. A novel laboratory scale method based on modeling, electrochemical testing, embedded electrode configuration will be designed, tested, and validated to develop tools to monitor and manage coating/substrate integrity applicable in the field. The integration of assessment tools and methods includes: (1) the deterministic relationship between the physical and chemical properties inherent in the (organic/inorganic) coatings and the transport mechanisms that are based on environmental parameters (leverage from FY11 corrosion assessment); (2) the testing technology that will follow the interfacial mechanisms and capture the stochastic nature of the environmental/structural variation when the metallic substrate is exposed to the corrosive environment and when it is intact; (3) high-resolution techniques that will characterize and quantify the damage or current state of the coating/substrate (leverage from FY11 unification of tools); (4) real-time monitoring that will quantify the measurements obtained with electrode configuration. The significant features of the proposed research are: (1) the development of the damage model/characterization methods will assist in the materials selection, coatings design and continuous monitoring of the state of the coating and the substrate when exposed in corrosive environments; (2) it will bridge the gap the theoretical deterministic-stochastic models with multi-scale experimental concepts, thus enabling the development of reliable monitoring tools to evaluate the integrity and reliability of coating/substrate as a system; (3) it will be the initial development of an algorithm /program for monitoring and management systems for continuous program (following phase II)

Task 1 Develop a simplified degradation and transport model for different coating/substrate systems Task 1a Develop theoretical framework of transport mechanisms with different damage (intact, semi

damage, damage) for primer, topcoat and conversion coatings Task 2 Develop a damage evolution model in continuous and cycling environment conditions by using

deterministic-stochastic modeling with design experimental laboratory testing. Task 2a Design laboratory testing of organic coating/substrate (steel, aluminum) and conversion

coating/substrate (steel, aluminum and magnesium) systems for validation of theoretical platform Task 2b – Develop damage evolution expressions based on environmental parameters, coating critical

properties and different coating damage states. Task 3 Design, test and verify novel monitoring system at a laboratory scale Task 3a Experimental design for field simulation conditions with distributed electrodes Task 4 Develop of a simple reliability model based on the integration of theoretical and experimental

results.

Task 4a Develop of a reliability model based on different failures modes (coating and metallic damage) using the developed damage evolution model and considering the associated uncertainties

Task 5 Identify a site, design the monitoring systems specific to the selected location Task 5a Customize the monitoring system to the selected location and application of the current

method/algorithm Product (deliverables):

• Insight into the damage evolution for coating, coating/metal interface and metal using non-intrusive and reliable method/algorithm, and verification through laboratory tests

• A basis for novel real-time monitoring of degradation/performance of the coating/substrate system to assist in establishing guidelines for coating/substrate system reliability.

• Verification of damage models and prediction methods using the new modeling/monitoring system to enable reliability based life cycle engineering

• The publication of findings in technical reports/scientific papers. • Participation in TCC meetings, technical conferences, electrochemical, coatings and corrosion forums.

Relevance and Cost of Corrosion Relationship: Relevance for this research include more reliable evaluation of coating systems service, and enhanced performance assessment and life prediction. Also, the objective is to contribute to a method or technologies used as monitoring or risk management tools of DoD assets. The definition and quantitative descriptions of damage evolution (shape and depth of corrosion) and the reliability model failure with different failure modes will be used for corrosion assessment, structural analysis and risk management for maintenance and repairing programs.

Project Title: Microbiologically Influenced Corrosion

Principle Investigator: Bi-min Newby

Work Statement: Our long term goals are to (1) develop more effective strategies to prevent and mitigate MIC and (2) develop reliable methods for predicting MIC. The specific objective of this project is to establish the correlations among metal (aluminum and carbon steel) corrosion, biofilm structure, and microbial metabolism in the well-defined systems which are essential for understanding MIC and developing better strategies for combating MIC in the real world complex environment. The tasks carried out in the project will provide the needed insights for corrosion mitigation of MIC, thus reducing the costs associated with microbial corrosion in many DOD applications where MIC has been found to be prominent including: pipelines/storage tanks, submarine cooling systems, power generation plants and fire sprinkler systems, and other aquatic structures. MIC is one of the worst forms of corrosion for metals, and it is often most difficult to identify and correct. It is believed that ~ 20% of the all corrosion on metallic material surfaces is related to MIC. Among many MIC systems, sulfate reducing bacteria (SRB) and fungi are two groups of most common species causing corrosion. Although SRB MIC has attracted numerous attentions in the field of corrosion, in many cases, the observed phenomena cannot be explained clearly by the current mechanisms. It is also found the existence of the fungi in the corroded fuel tanks, but mechanism of the corrosion is still clear. Due to the lack of the understanding of MIC mechanisms, the available methods for MIC monitoring, prediction, prevention and treatment are very limited. In this project, we aim to develop a better understanding on SRB and fungi MIC mechanisms in well-defined systems by correlating microbial metabolic activities, the spatial distribution of micro-organisms and metallic corrosion. The metabolism of a marine SRB strain (Desulfovibrio vulgaris) and a fungal strain (Trichoderma reesei), in the presence of carbon steel and aluminum, respectively, will be followed and correlated to the corrosion behaviors of each corresponding metal. We will use laser confocal scanning microcopy (LCSM) to monitoring the cell viability and spatial distribution of SRB biofilm on carbon steel and T. reesei biofilm on aluminum under both flow and stagnant conditions. The metabolism activity of both species will be studied in a flow system. Another focus of the project is to examine the spatial distribution of other three common environmental micro-organisms (Escherichia coli, Pseudomonas aeruginosa and Nitrosomonas europaea) and how they interact with each other in the mixed biofilm, and correlate the spatial distribution to the metallic corrosion. In our flow system the biofilm will grow from the surface and the continuous flow of the fresh diluted medium will maintain the growth of biofilm and wash out the detached bacteria cells. In our stagnant study, the diluted growth medium will be used and the cells will grow both on surface and in solution. For all studies, we have a parallel system as a control which contains sterile medium but no cell. The team is lack of expertise in electrochemistry analysis of metal corrosion. We will work with Dr. H. Castaneda-Lopez to incorporate the impedance and potentiostat sensors into the system to have a better understanding on the MIC from the view of electrochemistry. Relationship to the previous work: SRB corrosion study: In FY11 project, we identified SRB growth conditions and successfully grew SRB under the anaerobic condition. We performed a preliminary study on how the metabolic activity of SRB will affect carbon steel corrosion under the stagnant condition. In FY12 project, we will further investigate how SRB will affect carbon steel corrosion under different conditions (flow, pH and nutrients). Fungal corrosion study: In FY11 project, we built both flow and static systems to study fungal corrosion and we just performed an initial test for both systems. We are trying to solve the problems which occurred in the initial test. In FY12 project, we will correlate the metabolism of T. reesei, cell viability, biofilm structure, and associated microbial corrosion of aluminum.

Characterization of multi-species biofilm: In FY11 project, we mastered the technique to characterize biofilm structure of a single bacterial species using LSCM. In FY12, we will develop a procedure to characterize how multiple (i.e. 3) microorganisms interact with each other spatially in the biofilm.

Task 1: Correlate the metabolism of a marine SRB species (D. vulgaris), viability of the SRB in its biofilm (alive/dead cells distribution), biofilm structure and associated microbial corrosion of carbon steel

Task 2: Correlate the metabolism of the fungal strain (T. reesei), cell viability, biofilm structure and associated microbial corrosion of aluminum

Task 3: Develop a procedure to characterize how multiple microorganisms interact with each other spatially in the biofilm using laser scanning confocal microscopy (LSCM)

Task 4: Study how the environmental parameters (oxygen level, PH and nutrient level) will affect the biofilm structure, cell spatial distribution and cell viability of a multi-species biofilm and how biofilm will subsequently affect carbon steel corrosion using static and semi-flow systems

Task 5: Train at least two graduate students to conduct relevant MIC research Product (deliverables):

• Report on the validation of the SRB MIC mechanism • Report on conditions for growing biofilms of D. vulgaris and T. reesei • Report on the correlations among metabolism of D. vulgaris and T. reesei, cell viability, biofilm

structure, and carbon steel and aluminum corrosion. • Protocol for the characterization of multispecies biofilm • Technical report/publication(s) of findings • Participation in TCC meetings, technical conferences and corrosion forums • Quarterly progress reports • Trained graduated students who are qualified for MIC study

Relevance and Cost of Corrosion Relationship: It is believed that ~ 20% of the all corrosion on metallic material surfaces is related to MIC. Establishing the correlations between biofilm structure, microbial metabolism and MIC behaviors are essential for understanding MIC and developing effective strategies for combating MIC. The tasks carried out in the project should provide some needed insights for corrosion mitigation of MIC, thus reducing the costs associated with microbial corrosion.

Project Title: Localized corrosion and stress corrosion cracking of magnesium and magnesium alloys

Principle Investigator: H. Cong

Work Statement: The goal of this project is to elucidate the role of second-phase particles and alloying elements on the localized corrosion and stress corrosion cracking performance of high-strength and high-ductility magnesium alloys by means of a novel combination of state-of-the-art electrochemical and microscopy techniques that will allow electrochemical measurements at the micro-scale. The alloy systems to be evaluated include pure magnesium (control), Mg-Zr, Mg-Zn-RE, and Mg-Al-(Zn)-(RE), all of them commercially available. Experimental chemistries will be developed at Ohio State University, which will be included for characterization as well. Rare earth alloying elements to be considered include yttrium, lanthanum, and cerium. Solutions will include de-ionized water (control) as well as NaCl electrolytes of various concentrations and pH values. The macro-electrochemical characterization will be conducted using conventional electrochemical techniques including anodic and cathodic polarization scans, electrochemical impedance spectroscopy, and chronoamperometry. The micro-electrochemical characterization of the different alloys will be conducted using a novel approach based on electrochemical-atomic force microscopy (EC-AFM) scratching that allows the measurement of corrosion, pitting, and re-passivation potentials on individual second-phase particles. Temperature can also be controlled simultaneously during testing from freezing to around 65-70 ºC. The main advantage over more traditional techniques such as the micro-capillary electrochemical cell approach is that the measurements will be done in situ without the need for synthesizing inter-metallic particles. Eventually, this EC-AFM technique could be applied to synthetic inter-metallic compounds as well. Stress corrosion cracking mechanisms will be investigated by means of a modified constant load technique, in which the load is increased in small steps until approximately 90-95% YS as described elsewhere. Tests will be conducted at the open circuit potential (OCP) and at fixed potentials, which will relate to the pitting and re-passivation potential of the different second-phase particles.

Task No. 1: will focus on characterizing the macro-electrochemical behavior of the selected magnesium alloys. The overall effects of alloying elements and impurity content will be investigated here. Initial systems to be considered include: AZ31B, AZ91E, AM60, ZE41, AE44, and WE54.

Task No. 2: will focus on developing and implementing in situ EC-AFM scratching to study the electrochemical behavior of inter metallic and second-phase particles at the micro-scale. Corrosion, pitting, and re-passivation potentials of the individual phases will be measured during this task.

Task No. 3: will focus on studying the mechanisms of stress corrosion cracking under constant load with and without a net polarization. Product (deliverables): It is anticipated that this project will lead to a number of high-profile scientific publications that will greatly impact the corrosion and materials science communities. Moreover, the outcome of this investigation will aid in the design of new magnesium alloys with improved mechanical and corrosion properties for critical DoD applications by providing a better understanding of the role played by alloying elements and second-phase particles in corrosion and environmental cracking performance. Close interaction with other Universities is planned. In particular the project will be coordinated with work under development at The Ohio State University, currently led by Dr. Rudolph Buchheit. The work at OSU is focused on developing experimental alloy families rather than on existing commercial systems. In turn,

experimental alloys developed at OSU will be included for characterization in this project based on the progress of Dr. Buchheit’s work. Other deliverables include:

• Participation in TCC meetings, technical conferences and corrosion forums. • Quarterly progress reports. • Interaction with DoD Subject Matter Experts in material selection and design.

Relevance and Cost of Corrosion Relationship: Magnesium alloys could be one of the best options for lightweight armored vehicles, aviation, and missile systems. However, their intrinsic corrosion susceptibility limits their range of application. Specifically, the Army Research Laboratory plans to foster development of next generation high-strength Mg alloys (i.e. a minimum tensile strength of 500 MPa), high-ductility (approximately 15% ductility or greater), with superior corrosion resistance. The work proposed here compliments that which is being done by researchers at the Army Research Laboratory in Aberdeen, MD. The goal at ARL is to achieve a thorough understanding of the fundamental mechanisms by which lightweight armor alloys corrode using a suite of surface analytical techniques that include electrochemical atomic force microscopy (EC-AFM), scanning Kelvin probe microscopy (SKFPM), scanning electrochemical microscopy (SECM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), and eventually, secondary ion mass spectrometry (SIMS) and Auger electron spectroscopy (AES).

Project Title: Real time corrosion monitoring of microbially induced corrosion in water-cooling systems Principle Investigator: C. Monty Work Statement: The goal of this project is to develop a series of electrochemical and non-electrochemical techniques to determine, in real-time, whether microbial contamination of water-cooling systems and heat exchanges leads to microbially induced corrosion (MIC). MIC is one of the most insidious forms of corrosion and represents a significant threat to a large number DoD assets and operations. MIC is difficult to predict and monitor, but perhaps more importantly, it is extremely challenging to estimate if the activity of microbial communities associated with these assets will eventually result in accelerated corrosion. Water-cooling systems and heat exchangers are known to suffer microbial contamination to various degrees. In this regard, there is an added risk for DoD assets deployed for long periods of time in remote areas, especially if microbial activities result in rapid localized corrosion rates. Moreover, for certain corrosion resistant alloys (CRAs) used in pressure-retaining components there is always a possibility that localized corrosion will eventually transition into stress corrosion cracking (SCC). Therefore, assessing when microbial contamination of water-cooling systems could lead to MIC is of great scientific and technological significance. The ability to monitor the kinetics of MIC in real time is also paramount. Key objectives are to:

• Identify and isolate microorganisms common to a model water cooling system, • Evaluate a number of electrochemical and non-electrochemical techniques capable of detecting,

nondestructively, the initiation of microbial contamination and MIC, • Validate selected techniques in a number of electrolytes in the presence and absence of

microorganisms. Task 1 will be led by Dr. John Senko. This task will focus on identifying and isolating microorganisms

encountered in a model water-cooling system. Next-generation 16S rRNA gene sequencing approaches (pyrosequencing) will be used to evaluate the composition and structure of microbial communities associated with cooling water systems. Additionally, traditional culture-dependent approaches will be used to enumerate and isolate specific metabolic groups of organisms that could play a role in MIC. Examples include: i) acid-producing (ammonium or sulfur oxidizing or fermentative) and ii) sulfate- or Fe(III)-reducing bacteria]. We emphasize that since forms of microbial metabolism that could lead to MIC are phylogenetically widespread (e.g. sulfate-reducing bacteria are affiliated with Firmicutes and Deltaproteobacteria) it is difficult to identify specific species that could initiate MIC a priori. As such, enrichment and isolation of microorganisms will be guided by the prevailing physicochemical conditions of the systems as well as the organisms detected using nucleic acid-based community characterization. For instance, in our studies of microorganisms associated with FGD systems, enrichments of aerobic organotrophic bacteria were established in media that contained abundant sulfate and were incubated at 50°C. This enrichment approach was guided by the prevailing physicochemical conditions of the FGD absorber units as well as the detection of thermopilic and halophilic bacterial lineages in 16S rRNA gene sequence libraries obtained from the units. Our experimental approach has a number of clear advantages. In one hand, nucleic acid-based techniques for the analysis of microbial communities (e.g. 16S rRNA gene sequencing) allow us to evaluate the overall complexity of the microbial ecosystems. On the other hand, culture-dependent approaches allow us to minimize this complexity and evaluate the roles of specific metabolic groups of microorganisms in MIC. Given these considerations, the chemical composition (i.e. organic carbon content, major cation and anion concentrations) of cooling system fluids will be evaluated and used to guide enrichment and isolation efforts. The main

objective of this task will be to identify major microbiological “players” in cooling water systems, and their role in altering the corrosion behavior of selected alloys. Additionally, microorganisms that are recovered through culture-dependent approaches will be used for further studies (Task No 2 and No 3) aimed at elucidating electrochemical “signatures” that could be used to determine whether microbial proliferation leads to MIC.

Task No. 2 will be led by Dr. Mariano Iannuzzi, a core-corrosion faculty member at the National Center

for Education and Research on Corrosion and Materials Performance, in collaboration with Chelsea Monty, who has recognized experience in the area of electrochemical sensors and fuel-cells as well as expertise in turning beaker-scale assays into micro-scale/portable devices. This task will focus on evaluating a number of non-destructive electrochemical techniques as well as characterizing the electrochemical response of systems with and without microorganisms. The main objective of this task will be to determine whether microbial contamination will lead to microbially influenced corrosion of selected carbon and austenitic stainless steels as well as copper and nickel alloys.

The effect of different microorganisms on the corrosion resistance of carbon and austenitic stainless steels, selected cupronickel alloys, and nickel-based alloys will be investigated using cyclic polarization tests, linear polarization, electrochemical impedance spectroscopy, Mott-Schottky analysis, and weight loss. In addition, a mechanistic investigation will be conducted using a modification of the split-cell technique, which has been traditionally used in the evaluation of corrosion inhibitors [2]. In the split-cell approach, two electrodes are exposed to two independent environments, which are connected by a porous membrane. The porous membrane maintains ionic flow but temporarily prevents cross-contamination. The current flow and the electrochemical potential between the two working electrodes are determined by means of a zero resistance amperometer (ZAR). Initially, at time equal zero, the two half-cells will be filled with sterile solution. This will result on a very small current noise between the two identical working electrodes. At a given point in time, one of the half-cells will be inoculated with a particular strain of bacteria, which will alter the local electrolyte and, in turn, the direction and magnitude of the current flow. The direction and magnitude of the current flow will be, therefore, a quantitative measure of microbial activity. In addition, oxygen concentration, temperature, and solution agitation can be controlled independently on each half-cell. When used in conjunction with other techniques such as confocal microscopy, pH analysis, and REDOX potential measurements, the split-cell approach can provide mechanistic information, impossible to obtain by any other electrochemical technique.

Task No. 3 will be lead by Dr. Mariano Iannuzzi in collaboration with Dr. Monty and Dr. Senko. This

task will focus on evaluating possible probe designs for real-time corrosion monitoring based on the outcome of Task No. 2. Task No. 3 will benefit enormously from Dr. Monty’s experience on turning beaker-scale setups to small-scale commercial sensors. Possible approaches include modifications to the BioGEORGE system to mimic the split-cell setup. In this case, only one of the working electrodes will be exposed to the contaminated electrolyte, while the second one will remain under sterile conditions. The two working electrodes will be ionically connected by a porous membrane or by the selective deposition of an antifouling and anti-microbial coating. The system will monitor the electrochemical current between the two electrodes as a function of microbial contamination. Additional parameters to quantify will include local pH and REDOX potentials.

Product (deliverables): The outcome of this investigation will help elucidating one of the most challenging questions in MIC research, i.e. under which conditions microbial contamination of a particular system by a given community of microorganisms results on microbially induced corrosion.

This project will produce a number of scientific publication and laboratory procedures that will greatly impact the corrosion community.

It is expected that the outcome of this investigation could be readily implemented in a corrosion probe for real-time monitoring of microbial contamination and MIC.

This project will be conducted as a collaborative effort between the Department of Chemical and Biomolecular Engineering and the Department of Geology and Environmental Science.

Relevance and Cost of Corrosion Relationship: Microbially induced corrosion is an insidious form of corrosion that is difficult to detect. Moreover, it is extremely challenging to quantify the degree to which certain structures and components may be affected by MIC. There is, therefore, a significant risk associated with microbial activities related to corrosion, especially for critical DoD assets operating in remote areas for long periods of time.

Even though the field of MIC research has flourished over the years and the scientific community has now a much better understanding of certain fundamental aspects of the problem, it is still uncertain when processes associated with a given microbial community will result in general or localized corrosion. It is, therefore, of great technological significance to develop non-destructive techniques for monitoring the transition to MIC in real time.

Project Title: Real-Time In Situ X-ray Tomography Imaging of Crevice Corrosion Principle Investigator: S. Lillard Work Statement: Crevice corrosion studies to date have largely focused on the mass transport issue related to the Unanswered, however, are questions about the growth morphology of the crevice during propagation and if there is a synergy between the initiation of secondary sites and the propagation / passivation of the primary site. These questions arise because, until now, we have not been able to visualize this process. In this work we propose to image the initiation and propagation of crevice corrosion in corrosion resistant alloys in situ using real time x-ray tomography. The alloy to be investigated will be down selected from one of several with DOD applications including Inconel 686, Alloy 59, C-22HS. Tomography uses a series of two-dimensional X-ray image slices about a single axis of rotation to generate a three-dimensional reconstructed image of the inside of an object; it is identical in principle and in fact to CT X-ray scans of the human body however the image resolution is 10-50 times greater. Within this work, images will be taken during initiation and propagation of an artificial crevice fabricated from a chosen CRA. A proof-of-principle experiment will be initially carried out in real-time and in-situ at the Henry Moseley X-ray Imaging Centre within the School of Materials at the University of Manchester; this will provide image resolution of around 300-500nm. However, it is anticipated that a higher X-ray beam luminosity will be required to reduce the measurement time and increase the resolution to around 100nm. Such experiments will be performed on the X-ray Imaging and Coherence beamline I13 at the Diamond Light Source in Oxfordshire, UK. As reconstruction of the data collaboration is an experimentally challenging and mathematically intensive operation, our collaboration with Manchester will be critical to the success of this proposal. To realize the tomographic imaging of crevice corrosion work we will initially focus on the development of an electrochemical cell to be used in the beamline work. The cell will contain the artificial crevice as well as the traditional counter and reference electrodes used for corrosion electrochemistry experiments. As no tomographic investigations of crevice corrosion have been published, development of a cell geometry for a given beam orientation and imaging methodology will be necessary to provide the most clear images with no interference from the crevice joining fixture. As such several geometries will be developed in preparation for beamtime. In addition to this work we will also generate the necessary corrosion electrochemistry data for the CRA of choice. This will include potentiodynamic polarization curves in simulated crevice solution and artificial crevice assemblies to optimize exposure conditions for the tomography experiments. These data will also be used as input for our crevice corrosion damage evolution model. The program is designed to take place over three fiscal years. The tasks to be completed each year are as follows: FY1

Task 1 - Technical scope activities including preliminary tomography cell design Task 2 - Initial corrosion electrochemistry data on downselected CRA Task 3 - Initial tomography measurements

FY2 Task 1 - Analysis of tomographic data Task 2 - Refining of tomography cell design Task 3 - Additional corrosion electrochemistry data Task 4 - Additional tomography measurements

FY3 Task 1 - Incorporation of initial data in crevice 3-D corrosion damage model Task 2 - Additional tomographic measurements Task 2 - Final analysis of tomography data

Product (deliverables): As a result of this project we will 1) determine the growth morphology of propagation as a function of time and 2) determine if there is a synergy between the primary initiation sites and the propagation / passivation of secondary sites. Not only will the result of this work answer fundamental questions about the mechanism of

crevice corrosion in CRAs, but it will also serve to benchmark our mass transport model of crevice corrosion that we are developing under separate funding. Ultimately we hope to build a full 3 dimensional model of the crevice corrosion of CRAs that will account for this behavior. The results of this model will then be used to design engineering assemblies to minimize crevice attack or predict service lifetimes. Other deliverables include:

• Preparation of UCC Project presentations for participation in UCC meetings, technical conferences and corrosion forums.

• Project progress reports. • Publications and presentations • Technical assessment of findings and recommendations for continued development.

Relevance and Cost of Corrosion Relationship: Descriptions of crevice corrosion damage evolution and its relationship to CRA performance are needed for informed design to avoid or to mitigate corrosion, as well as for materials selection. Improved design for corrosion mitigation, maintenance procedures and sustainability strategies can greatly reduce the costs of corrosion and improve availability.

Project Title: Evaluation of Galvanic Corrosion Principle Investigator: S. Lillard Work Statement: The overall goal is to apply, advance and develop commercial software and UA computational modeling code to predict damage evolution from galvanic corrosion. This FY12 project is primarily an experimental endeavor and complement to the UA modeling work. The results are to demonstrate and validate the models and software. The work will progress from uncomplicated, baseline configurations to more complex geometries and galvanic action in multi-layer structures. The experimental tasks are to measure (a) basic corrosion properties (corrosion potential, polarization behavior and solution conductivity) and (b) galvanic action for realistic and model assemblies (galvanic couple potential, galvanic currents, potential and current distributions, evolution of environments). Two DoD applications with galvanic effects from fasteners are targeted:

• High strength fastener materials for navy applications (alternatives to Monel K-500) • Fasteners in aluminum sheet/structure in aircraft

The naval application will incorporate alloys and geometries relevant to NSWCCD in their fastener replacement program. The aircraft application will examine steel and Corrosion Resistant Alloy (CRA) fasteners in aluminum sheet and plate. For both applications, the geometries and materials combinations selected will be analyzed using GalvanicMaster a commercial software product by Elsyca and the UA computational modeling code. The incorporation of damage evolution in the UA code is a “leap forward” in models of galvanic corrosion and will enhance the understanding of interactions among various corrosion degradation processes, e.g. galvanic corrosion leading to crevice corrosion and stress corrosion cracking. As such, the focus will be on the early stages of galvanic corrosion damage and potential for transitions among degradation modes. Task 1: Interact with UA and other TCC (university and DoD labs) galvanic corrosion and relevant crevice

corrosion projects. Task 2: Measure additional (beyond that from current projects) basic corrosion and electrochemical properties

for applications: corrosion potential, polarization behavior and solution conductivity. Materials include steel, representative CRAs and copper alloys, and aluminum.

Task 3: Develop and demonstrate uncomplicated, baseline configurations for galvanic corrosion experiments (a) stack tests and (b) disc on plate tests. The stack configuration comprises a number of metal washers and spacers. The disc on plate configuration comprises washers on plate or embedded rod in plate. These are to be fabricated with contiguous metal-metal contact or with electrical isolation between metals and external electrical coupling. The latter allows measurement of current distribution as well as potential profiles.

Task 4- Measure galvanic action for assemblies designed to test validity of model and software predictions: galvanic couple potential, galvanic currents, potential and current distributions, evolution of environments. The corrosion damage profiles are measured after the exposure and compared with predictions of UA computational code. Galvanic couples include steel/copper, steel/CRAs, and steel/aluminum.

Task 5: High strength fastener materials for navy applications (alternatives to Monel K-500) 5.1 Select materials and develop model geometries relevant to NSWCCD project. Treat the target application in multiple steps with increasing complexity. 5.2 Measure galvanic action for assemblies designed to test validity of model and software predictions. 5.3 Measure galvanic action for relevant NSWCD assemblies. 5.4 Interact with UA and other TCC (university and DoD labs) galvanic corrosion projects and other relevant crevice corrosion projects.

Task 6: Fasteners in aluminum sheet/structure in aircraft 6.1 Select materials and develop model geometries relevant to fasteners in aluminum. Treat the target application in multiple steps with increasing complexity. 6.2 Measure galvanic action for assemblies designed to test validity of model and software predictions.

6.3 Measure galvanic action for relevant assemblies. 6.4 Interact with UA and other TCC (university and DoD labs) galvanic corrosion projects and other relevant projects for corrosion and coatings.

Project Title: Development of a Steel Reinforced Concrete Corrosion Monitoring and Management System Principle Investigator: A. Patniak Work Statement: Corrosion of steel reinforced concrete (RC) used for immovable defense and civilian infrastructure and assets is a serious problem. The earlier fiscal year projects on RC corrosion devoted efforts in developing the understanding of uniform and non-uniform steel corrosion in reinforced concrete through experiments and computational modeling. A multi-scale approach was taken to address the effects of uniform and non-uniform corrosion rate and formation of corrosion products on concrete degradation, bond strength (pull-out of steel from concrete) and flexural performance. Assessment of current technology revealed that there are many limitations of the currently used corrosion monitoring and management systems for steel reinforced concrete including unreliable data, high installation and maintenance costs. Cost effective alternative routes are needed to detect, monitor and manage RC corrosion. Quantitative evaluations of corrosion related deterioration are required for performance assessment, structural design, preventive maintenance, remaining life prediction, and risk management. A novel laboratory scale concrete corrosion test cell based on embedded sensor configuration will be designed, tested, and validated in this project to monitor RC corrosion. Uniform and non-uniform corrosion along the embedded steel reinforcing bars will be captured with the new sensor systems. Potential measurements will be made at strategically placed sensors with Ti/RuO2 electrodes under steady state and no polarization conditions. New testing based on sensors will bridge the gap between the previous calculations for non-uniform corrosion with current dissolution and real time monitoring parameters. Corrosion monitoring and management systems will be developed with emphasis on damage assessment, reliability, risk assessment, and remaining life predictions.

Task 1: Develop a conceptual framework for a non-intrusive, robust and reliable monitoring system based on previous modeling and current experimental work

Task 2: Design, fabricate, test and verify the new monitoring system at a laboratory scale Task 3: Conduct designed experiments and collect data for verification of the monitoring system at a

laboratory scale Task 4: Identify a bridge, design the monitoring systems specific to the selected bridge, and install the

sensor system for the collection of field data Task 5: Analysis of field data and verification of accuracy along with correlation with laboratory data

and system design while considering of reliability, and risk assessment Task 6: Establish concrete degradation and residual strength functional (semi-empirical) expressions,

understand cracking and strength behavior and life cycle performance based on the data collected with the new monitoring system

Task 7: Documentation of the experimental and theoretical research performed in the project Product (deliverables): • A new monitoring system design, test data, and validation for potential field implementation • Insight into the corrosion rate using non-intrusive and reliable monitoring system, and verification through

laboratory tests • Verification of damage/degradation models and prediction methods using the new monitoring system to

enable reliability based life cycle engineering • Technical report/publication(s) of findings • Technical assessment of findings and recommendations for continued development • Participation in TCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: Corrosion of steel reinforcement embedded in concrete structures and the related degradation is a common problem particularly in coastal and saline environments. Corrosion monitoring of a reinforced concrete system has great benefits with applications both in the defense and civilian sectors. This project is aimed at providing a corrosion monitoring and management system to

combat RC corrosion in infrastructure sector. Relevance of this research includes a more reliable system for corrosion assessment and life prediction so as to reduce life cycle costs resulting in longer useable life span of infrastructure and moderated maintenance costs (ROI).

Project Title: Self-Stratifying Corrosion Resistant Coatings Principle Investigator: M. Soucek Work Statement: This work builds on the previous “Organic Coating Interaction with non-standard Metals or Alloys.” The same primers which were used as a one step pretreatment primer coating will be utilized with either an acrylic or non-isocyanate polyurethane topcoat. The project will start with common alloys such as 2024 Al and steel, and work to the newer alloys or different metal such as magnesium and titanium. There will be two thrusts in this project: 1) preparation of coated samples for exposure (accelerated Ohio State University, OSU, and outdoor University of Hawaii, UH, weatherometer at UA), 2) Evaluation of exposed coatings at University of Akron using both spectroscopic and wet chemistry techniques. The self-stratifying inorganic/organic corrosion resistant coatings will be prepared for exposure on a variety of metal substrates including typical aluminum and steel substrates as well as magnesium titanium and emerging alloys. These samples will be sent to UH for environmental exposure and OSU for accelerated exposure. The concept is to gain an understanding of how changing the substrate changes the interaction and corrosion protection of the coating. Microscopy specifically SEM and TEM will be used in conjunction with AFM and XPS. Stratification of the coatings will be evaluated using XPS, and cross-sections of elemental mapping using EDAX-SEM. Cross-sections can be evaluated to ascertain the generation of metal ions in the organic films. The interface between the coating and the metal substrate will investigated using grazing (x-ray and/or neutron, IR) techniques. Conventional spectroscopy IR, NMR ( liquid and solid state), and MS will be used supplement the grazing techniques and give insight into any change in the bulk properties of the organic coating. Both model samples of silicon wafer with vapour deposited metal of choice, and standard metal coupon samples will be used. The model samples will be exposed with the coupons. The necessity of the model samples is that for the state of the grazing spectroscopy to capture the nano-meso region of the interface, the samples have to be perfectly flat, thus the silicon wafers.

Task 1: Prepare Acrylic Topcoats, Epoxide primers for self-stratified coatings Task 2: Adjust parameters for Curing: Crosslinker, Catalysts, and Thermal condition, Solvent selection Task 3: Evaluate curing of Primer and Topcoat separately. Task 4: Exposure of Topcoat using Weathering, UH (outdoor), OSU (Salt Spray) After Exposure,

Coating testing performed at (UA) Task 5: Evaluate Samples from exposure: IR, Raman, gloss, corrosion resistance

Product (deliverables): -­‐ Proof of concept for standard metals -­‐ Concepts translated for other systems -­‐ Samples to internal TCC and DOD participants -­‐ Quarterly reports Relevance and Cost of Corrosion Relationship: To replace 2 or more coatings steps with one application of a coating that performs as well or better than the multi-step process saves the DOD time and money. Time is saved in that there is only one coatings application that replaces a separate pretreatment, primer, and topcoat steps. Instead or three to fours days in a coating process, a self-stratifying system will take only 1 day. The cost of coatings includes both the labor and the materials; and the labor is far more expensive with respect to both substrate preparation, application time, and drying/curing time, than the cost of the coating itself. The in-situ pretreatment can be less demanding than standard pretreatments which means that these systems may be used more effectively in the field without little or no surface preparation. A self-stratifying coating represents a labor savings of at least 66%. Since the DOD is moving toward the usage of newer higher performance alloys, there is a need to understand how self-stratifying coatings can be translated to newer alloys and composite systems. Visited ARL and they thought that this was an area that we could demonstrate the coating for the DOD.

Project Title: High Performance Alkyd Coatings Principle Investigator: M. Soucek Work Statement: Alkyds have been and will be used as a protective coating for DOD. Due to environmental regulations in eliminating organic solvent coupled with a lack alkyd development by coating companies, alkyds are slowly being replaced with coatings that are less effective at a higher cost. This project will focus upon two thrusts in alkyd technology: 1) High solids with reactive diluents, 2) Waterborne. The high solids approach will have a self-stratifying component where an alkyd based corrosion resistant primer/ pretreatment will be used with a partially fluorinated alkyd topcoat. The alkyds will partially phase separate driven by the interfacial chemical potential, resulting in the alkoxylsilane alkyd dominating the film substrate interface and the fluorinated alkyd dominating the film air interface. The waterborne alkyd will be water-reducible where a stable alkyd-acrylic is formulated with reactive diluents and dispersed in water. The focus of these coating will be munitions and Naval ships. There will interaction with ARL for the munitions with respect to both sharing samples and coating munitions at ARL. The alkyds will be coated over principally steel with some Al. These samples will be sent to ARL and OSU for accelerated exposure. Microscopy specifically SEM and TEM will be used in conjunction with AFM and XPS. Stratification of the coatings will be evaluated using XPS, and cross-sections of elemental mapping using EDAX-SEM. Cross-sections can be evaluated to ascertain the generation of metal ions in the organic films. Corrosion will be evaluated using scribed panels. Other standard coatings properties will be evaluated such as adhesion, crosslink density, hardness, flexibility, Tg, chemical resistance, abrasion resistance, and other tests as appropriate.

Task 1: Prepare Alkyds and reactive diluents for Topcoats, Alkoxy and TEOS modified Alkyds and reactive diluents fro primer/pretreatment. primers for self-stratified coatings

Task 2: Coat substrates, Evaluate Coatings, Evaluate Coatings for Stratification Task 3: Evaluate Coatings for pot-life stability Task 4: Exposure of Topcoat, primer, and topcoat/primer using Weathering, UH (outdoor), ARL (Salt

Spray) After Exposure, Coating testing performed at (UA) Task 5: Evaluate Samples from exposure: IR, Raman, gloss, corrosion resistance

Product (deliverables): -­‐ Proof of concept for self stratifying high solids alkyds. -­‐ Stable, Inexpensive, waterborne alkyd coating -­‐ Samples to internal TCC and DOD participants -­‐ Quarterly reports Relevance and Cost of Corrosion Relationship: Alkyds have been used as a mainstay in DOD maintenance coatings for many years, unfortunately alkyd technology has not kept up with the DOD coating needs. For the high solids self-stratifying alkyd, to replace 2 or more coatings steps with one application of a coating that performs as well or better than the multi-step process saves the DOD time and money. Time is saved in that there is only one coatings application that replaces a separate pretreatment, primer, and topcoat steps. Instead or three to fours days in a coating process, a self-stratifying system will take only 1 day. The cost of coatings includes both the labor and the materials; and the labor is far more expensive with respect to both substrate preparation, application time, and drying/curing time, than the cost of the coating itself. The in-situ pretreatment can be less demanding than standard pretreatments which means that these systems may be used more effectively in the field without little or no surface preparation. A self-stratifying coating represents a labor savings of at least 66%. With respect to the waterborne alkyds, the self-life stability, the lack of VOCs and HAPs, and improved performance will result in an upgrade in performance without having to move to an entirely different coating system.

Project Title: Model for Crevice Corrosion Damage Evolution Principle Investigator: G. Young

Work Statement: The goal of this project is to formulate, analyze and solve mathematical models for crevice corrosion damage evolution for Ni base alloys. Crevice corrosion is an issue in many DoD platforms and the proposed investigation will assist in establishing design guidelines for DoD components susceptible to crevice corrosion. Specific investigations will focus on crevice corrosion of high strength fastener materials. The knowledge gained through mathematical modeling and simulation coupled with an experimental plan of investigation provides insight into the fundamental mechanisms underlying crevice corrosion and means to prevent it, and improve our ability to predict metal component performance assessment and life. This work was initiated with FY10 and FY11 funds. The models receive input from and validation by laboratory experiments that measure different stages of the corrosion process, such as initiation, propagation, stifling (corrosion slows) and arrest (corrosion stops). Experiments provide direct measurement of corrosion rates, characterization of interface processes, electrochemical tests for dissolution evolution, and supplemental tests to determine properties of solutions and deposits that affect active and passive states. In turn the models identify material parameters, environmental and system variables that need to be measured. Samples exposed to field environments will be used for model testing and define in advance what specific metrics should and can be obtained from such samples. Key objectives are to:

• Advance the understanding of localized corrosion mechanisms • Assist in establishing guidelines for initiation and propagation of the crevice corrosion process • Identify control actions to slow (stifle) and/or stop (arrest) crevice corrosion

Two sets of models (identified as a[FY10, FY11], and b[FY11, FY12]) are being developed to investigate the corrosion in a thin crevice established between a metal surface and the crevice former. The models represent stages of increased complexity as assumptions are relaxed and features added. The a models define the mathematical modeling and computational framework for the investigations of crevice corrosion damage evolution in pure metal systems in sulfuric acid (consistent with published laboratory investigations). Alloy systems in seawater or atmospheric conditions are the focus of the b models. A long-term objective of the FY10, 11 and 12 investigations is to formulate, analyze and solve a mathematical model for corrosion damage evolution in a high strength fastener system composed of dissimilar metals. It is conjectured that both galvanic and crevice corrosion mechanisms will be active in such systems. Due to the complexity of this interaction, the modeling will progress through three stages of development. In the first stage the crevice former will be an insulator material so that galvanic couples are missing. Here the focus is solely on crevice corrosion. In the second stage the crevice former will be from the same material as the underlying metal. Again crevice corrosion is the focus, however, corrosion damage of the crevice former will be included in the stage two investigations. Finally, the crevice former will be from a different material than the metal. Hence, we anticipate both crevice and galvanic corrosion mechanisms will be active. We note that the University of Akron investigating team for this crevice corrosion project is also involved with a companion project for galvanic corrosion. The latter project isolates galvanic corrosion from crevice corrosion, while the project described above isolates crevice corrosion from galvanic corrosion. Knowledge from both projects is combined in stage three. Further, there are also companion projects at The University of Akron focusing on laboratory investigations of crevice corrosion damage evolution. While these projects are not listed or discussed here, the work of all companion projects will proceed hand-in-hand with the modeling investigations.

STAGE I – CREVICE FORMER IS AN INSULATOR MATERIAL a Models

a Model [FY10]. This initial model focused on a one-dimensional equation defining the system potential, coupled with a two-dimensional damage evolution equation of the metal surface, in a pure metal system (Nickel in sulfuric acid) under a well-mixed assumption both outside and within the crevice. Consistent with experimental simplifications, the metal surface (outside the crevice) for cathodic reduction was kept at a constant potential. Hence, the only reaction accounted for in the model was the anodic dissolution reaction of the pure metal substrate. Model simulation results are consistent with published experimental results. a Model [FY11]. The a model is being extended to a two-dimensional equation defining the system potential, coupled with a two-dimensional damage evolution equation of the metal surface. Preliminary results show the one-dimensional model predictions to be in agreement with the two-dimensional model predictions for corrosion damage on the order of the initial crevice gap or less. The one-dimensional model begins to lose accuracy as the magnitude of the damage increases beyond the size of the initial gap.

b Models (FY11)

While the a models focus on pure metal systems, the b models focus on corrosion resistant alloys. Similar solution methodologies as the a models are used. Alloys to be considered will be consistent with the joint NSWC project: high strength Ni-Cr-Mo alloys such as Inconel 686, Alloy 59, C-22HS that have been identified as suitable replacement candidates for Monel K-500. b1 Model [FY11]: This model investigates the same geometrical configuration as the a model. However, the well-mixed assumption is only posed outside the crevice. Hence, ionic species transport by diffusion and ion migration is included within the crevice. Reactions for the anodic dissolution of the metal substrate and the hydrolysis of the metal cations are included. The species transport model is simplified using a dilute system approximation. b2 Model [FY11]: This model investigates atmospheric crevice corrosion by assuming a thin film electrolyte on the metal surface outside the crevice. The constant potential assumption is no longer included. Hence, reactions for the anodic dissolution of the metal substrate, the hydrolysis of the metal cations, dissociation of water, and cathodic reduction of oxygen, hydrogen ions and water are included. b3 Model [FY11]: This model investigates the same species and reactions as the b2 model. However, the crevice former is completely immersed in liquid for this case.

STAGE II – CREVICE FORMER IS THE SAME MATERIAL AS THE UNDERLYING METAL STAGE III – CREVICE FORMER IS A DIFFERENT MATERIAL THAN THE UNDERLYING METAL b Models (Proposed FY12)

The b models will be extended to crevice formers of the same and dissimilar materials. In addition more accurate transport models that relax the dilute approximation will be developed. Material properties will be obtained from OLI software.

The FY12 work builds on and extends FY10 and FY11 work and comprises the following:

Task 1 Formulation and solution of an enhanced damage evolution model (b2), including oxygen and multiple ionic species, for an alloy system in a thin electrolyte film environment outside the crevice accounting for crevice and galvanic corrosion mechanisms for fasteners composed of dissimilar metals – to be started December 2012.

Task 2 Formulation and solution of an enhanced damage evolution model (b3), including oxygen and multiple ionic species, for an alloy system in a fully immersed environment outside the crevice

accounting for crevice and galvanic corrosion mechanisms for fasteners composed of dissimilar metals – to be started December 2012.

Task 3 Comparison with experiments, model validation and model refinement – to be started in June 2013.

Task 4 Validation of model for alloy systems - to be started in June 2013. Task 5 Compilation of data for model inputs (continuing). Special attention will be paid to comparing

model results with data from the NSWC studies on crevice corrosion of high strength fastener materials.

Task 6 Compilation of experimental results for model inputs and validation (continuing). Task 7 Technical assessment of findings and recommendations for continued development – to be

started in Dec 2013. Product (deliverables): The knowledge gained through mathematical modeling and simulation coupled with an experimental plan of investigation provides insight into the fundamental mechanisms underlying crevice corrosion and means to prevent it, and improve our ability to predict metal component performance assessment and life. Hence, outcomes of the research are:

• Formulation and solution of enhanced b models for damage evolution in an alloy system • Plans for iterative model development with evolving treatment of more complex systems • Compilation of data for model inputs • Technical report on the testing and validation of the b models • Compilation of experimental results for model inputs and validation, including comparison with any

relevant data from NSWC studies on crevice corrosion of high strength fastener materials • Technical assessment of findings and recommendations for continued development • Participation in TCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: Crevice corrosion is difficult to detect because it develops in narrow gaps formed by bolt heads and lap joints, for example, with a metal surface. Materials (stainless steels, titanium and aluminum) that usually do not corrode under normal circumstances can be damaged in a crevice corrosion environment. Catastrophic structural failure can occur in situations where corrosion is unexpected or undetected. While much progress has been made in understanding crevice corrosion initiation, propagation (damage evolution of the metal surface) is less characterized. Only limited progress has been made for quantitative descriptions of damage evolution (shape and depth of corrosion), and this information is required for enhanced performance assessment, structural analysis and risk management.

Project Title: Role of Non-Uniform Corrosion Prod Growth on Steel Degradation

Principle Investigator: A. Patnaik

Work Statement: Deterioration  of  concrete  infrastructure  because  of  corrosion  of  steel  reinforcement  has  been  recognized  for  several  decades  as  a  major  technical  and  economic  challenge  in  the  United  States.  One  particular  aspect  is  the  degradation  of  the  elements  of  the  cell  naturally  formed  by  the  concrete  and  the  metallic  rebar.  Rebar/concrete  interface  has  been  characterized  and  modeled  by  many  researchers.  Due  to  the  heterogeneous  distribution  of  the  chemical  species  and  compounds  in  concrete,  development  of  non-­‐uniform  corrosion  products  in  concrete  leads  to  localized  attack  and  decreases  durability  of  concrete  structure  under  loading.  

Multi-­‐Scale  modeling  of  a  system  from  the  corrosion  process  (micro/meso  scales)  to  full  system  performance  (macro/mega  scales)  has  great  benefits.  The  primary  objective  of  the  project  is  to  advance  the  understanding  of  uniform  and  non-­‐uniform  steel  corrosion  in  reinforced  concrete  through  coordinated  experiments  and  computational  modeling.  A  multi-­‐scale  approach  is  taken  to  address  the  effects  of  uniform  and  non-­‐uniform  corrosion  rate  and  formation  of  corrosion  products  on  concrete  degradation,  bond  strength  (pull-­‐out  of  steel  from  concrete)  and  concrete-­‐steel  interface.    

Several  models  describe  the  concrete/rebar  interface  behavior  by  validating  the  coupling  of  theoretical  and  laboratory  experiments  that  measure  different  stages  of  the  damage  process,  such  as  initiation,  transition  and  propagation  of  corrosion.    Experiments  provide  direct  measurement  of  chloride  diffusion  rates,  corrosion  rates,  characterize  interface  processes,  and  properties  of  solutions  and  deposits  that  affect  the  interfacial  dissolution  and  passivation  mechanisms.  

The  effort  of  multi-­‐scale  studies  (Task  FY11-­‐1A)  is  organized  as  follows:  

Task  1:    Develop  a  conceptual  framework  for  multi-­‐scale  treatment  of  uniform  and  non-­‐uniform  steel  corrosion  in  reinforced  concrete.  

Task  2:    Computational  treatment  of  the  micro/meso  scale  with  models  considering  chemical  composition,  and  rate  and  extent  of  corrosion  along  with  volume  changes.      

Task  3:    Experimental  treatment  of  the  micro/meso  scale  to  study  the  effects  of  chlorides  in  concrete,  and  localized  impressed  current  to  address  the  non-­‐uniform  corrosion  rate  and  formation  of  corrosion  products.  

Task  4:    Computational  treatment  of  macro/mega  (element/system)  scale  to  simulate  uniform  and  non-­‐uniform  corrosion  of  steel  reinforcing  bars  within  concrete.  

Task  5:    Experimental  treatment  at  the  meso  (element)  scale  to  establish  the  rate  of  growth  and  chemical  composition  of  corrosion  products  grown  at  different  corrosion  rates  and  environmental  conditions.  

Task  6:  Establish  concrete  degradation  and  residual  strength  models,  understand  cracking  and  strength  behavior  and  life  cycle  performance  at  different  scales.  

Product (deliverables):

Task  FY11-­‐1A:  Multi-­‐scale  Studies    

• Insight  into  degradation  mechanisms  of  steel  reinforced  concrete  due  to  uniform  and  non-­‐uniform  reinforcement  corrosion  

• Multi-­‐scale  experimental  evaluation  methodology  based  on  accelerated  and  natural  corrosion  testing  and  methods  for  quantifying  damage  

• Insight  into  the  multi-­‐scale  effects  of  rate  and  amount  of  corrosion,  and  composition  of  corrosion  products  on  corrosion  damage  

• Damage/degradation  models  and  prediction  methods  to  enable  reliability  based    life  cycle  engineering  of  reinforced  concrete  structures  

• Formulation  of  computational  models  for  evolution  of  non-­‐uniform  corrosion    Task  FY11-­‐1B:  Micro-­‐Scale  Corrosion  Test  Cells  

• Basis  for  development  of  microscale  samples  of  degradation/performance  of  the  reinforced  concrete  system  to  assist  in  establishing  guidelines  for  initiation,  transition  and  propagation  stages  of  the  damage  process  

• Demonstrate  the  application  of  test  cells  to  control  non-­‐uniform  growth  of  corrosion  products  on  steel  in  concrete  

• Set-­‐up  and  validate  a  multi-­‐test  station  rig  for  concrete  corrosion  tests    

Publications  and  Reports  

• Technical  report/publication(s)  of  findings  • Technical  assessment  of  findings  and  recommendations  for  continued  development  • Participation  in  UCC  meetings,  technical  conferences  and  corrosion  forums  • Quarterly  progress  reports  

Relevance and Cost of Corrosion Relationship: Corrosion  of  steel  reinforcement  embedded  in  concrete  structures  and  the  related  degradation  is  a  common  problem  particularly  in  coastal  and  saline  environments.    Modeling  of  a  system  from  the  corrosion  process  to  full  system  performance  has  great  benefits  for  infrastructure  and  asset  management  with  applications  both  in  the  defense  and  civilian  sectors.    Quantitative  evaluations  of  corrosion  related  deterioration  are  required  for  performance  assessment,  structural  design,  preventive  maintenance,  remaining  life  prediction,  and  risk  management.  

Project Title: Risk Assessment for Steel Structures

Principle Investigator: G. Young

Work Statement: This objective is to apply and enhance the risk assessment of corrodible structures for the application to steel structures. Basis for corrosion damage of structural grade steels such as ASTM A36 and A992, and bolted and welded structural steel connections will be developed in this project. The effects of corrosion rate and formation of corrosion products on the degradation process and metal loss will be studied along with protection methods. Metal loss will be evaluated along with the study of the influence of general (uniform) corrosion, localized corrosion, and non-uniform patterns of pitting corrosion on the stresses and strains within the elements of structural steel members and connections. Degradation of steel structures and connections due to non-uniform corrosion of the elements of steel structures and connections, prediction of the residual strength, and the determination of the remaining life of deteriorating structures in a multi-scale approach is needed to develop reliable and meaningful design methodologies of steel structures that are degrading due to corrosion.

Task 1: Identify candidate corrodible systems for consideration in consultation with UCC/TCC participants, other DoD contacts and industry/government contacts. Down select an application for this effort.

Task 2: Identify the tools and develop an approach for risk assessment to be applied for the selected corrodible system.

Task 3: Identify corrosion risks and mitigation (barriers) to risks.

Task 4: Identify methods and apply them to corrosion damage evolution for the selected application.

Task 5: Apply risk assessment to a case study to determine current status and make projections of future performance with alternative corrosion control strategies.

Task 6: Integration with FY11-2A, Corrosion Damage and Remaining Strength of Steel Structures

Product (deliverables):

• Selection of an application suitable to demonstrate the benefits of enhanced treatment of “Risk Assessment of Corrodible Systems” Task 2: Identify the tools and develop an approach for risk assessment to be applied for the selected corrodible system.

• Technical review of corrosion risks and mitigation (barriers) to risks. • A review of methods and application to corrosion damage evolution for the selected application. • Develop a case study for risk assessment to determine current status and make projections of future

performance with alternative corrosion control strategies. • Integration with FY11-2A, Corrosion Damage and Remaining Strength of Steel Structures • Technical report/publication(s) of findings • Technical assessment of findings and recommendations for continued development • Participation in UCC/TCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: Corrosion of steel structures and connections is a common problem particularly in coastal and saline environments. Modeling of a system from the corrosion process to the system performance has great benefits for infrastructure and asset management with applications both in the defense and civilian sectors. Quantitative evaluations of corrosion related deterioration are required for performance assessment, structural design, preventive maintenance, and risk management.

Corrosion of structures made from carbon steels and other common grade steels including bolted and welded connections has great influence on lifecycle costs of DoD assets, particularly Naval assets, in coastal environment and saline environment. Sheet piles and exposed piles in marine environment, bulkheads and decking frames of naval ships, are some of the examples of steel structures susceptible to corrosion.

Project Title: Evaluation of Galvanic Corrosion

Principle Investigator: S. Lillard

Work Statement: The objective of this work is to examine galvanic corrosion and to extend the typical treatments to consider more realistic conditions. The extended conditions include complex shapes and structures, more complex and broader range of environments, thin films of electrolyte rather than fully immersed conditions, temporal changes in the environment and the metal surface, and multi-metal/conductor assemblies. The effort will include experimental measurements and analytical, computational modeling.

The computational modeling will use commercial software packages to determine behavior of simple and complex galvanic couples. Computational results will be tested and validated by experiment. The experimental tasks will measure (a) fundamental behavior (corrosion potential, polarization behavior and solution conductivity) and (b) galvanic action for realistic and model assemblies (galvanic couple potential, galvanic currents, potential and current distributions, evolution of environments). The study will be focused on applications of interest to DoD, e.g. fasteners in aluminum sheet/structure, galvanic action of multi-layer structures and interactions of galvanic action, cathodic protection and environmental cracking.

Typically baseline galvanic corrosion action is measured by potential difference between the two metals that are fully immersed in a solution (often 3.5% NaCl or the like). More complete treatment can be based on polarization behavior in the solution. So, the baseline galvanic action between metals is measured anodic and cathodic polarization curves of each of metal is obtained by potentiodynamic polarization. Based on the mixed potential theory, the behavior of the component materials in a galvanic cell is predicted. Galvanic current between the couples is measured with a zero-resistance ammeter, and the potential of the couples is measured over time.

The baseline theoretical predictions are compared to measured behavior of galvanic couples between metals. From the polarization curves the galvanic behavior of these metals is predicted based on the mixed potential theory. First, based on corrosion potential, the anode and cathode of the galvanic cell are determined. The electrode with more positive corrosion potential (Ecorr) is the cathode and the one with more negative Ecorr is the anode in a galvanic couple. Second, the sum of anodic oxidation currents must equal the sum of cathodic reduction currents. Based on this, the rest state of the galvanic couple is the point where total anodic polarization curve intersects with total cathodic polarization curve in the E-logi diagram.

Task 1: Select and train with commercial software, e.g. Elysca Inc.

Task 2: Develop list of DoD relevant applications and select target application(s) for study

Task 3: Model baseline galvanic couple geometries

Task 4: Model of target application in multiple steps with increasing complexity

Task 5: Measure fundamental metal/solution behavior, e.g. corrosion potential, polarization behavior and solution conductivity

Task 6: Measure galvanic action for realistic and model assemblies, e.g. galvanic couple potential, galvanic currents, potential and current distributions, and evolution of environments.

Task 7 Examine relationships among galvanic action, cathodic protection and environmental cracking.

Product (deliverables):

• Outcomes for each of the task above. • Preparation of UCC Project presentations for participation in UCC meetings, technical conferences and

corrosion forums.

• Project progress reports. • Publications and presentations • Technical assessment of findings and recommendations for continued development

Relevance and Cost of Corrosion Relationship: This project is relevant to corrosion management for reduced costs and increased reliability. Current baseline treatments for design and control of galvanic action, e.g. tables of galvanic potential, are too simplistic for forecasting realistic galvanic action and risk of corrosion damage. The findings inform procedures for monitoring and detection of detrimental corrosion effects, maintenance protocols for remediation and mitigation, and methods for corrosion prevention and control.

Project Title: Damage Evolution Modeling & Computational Simulation

Principle Investigator: G. Young

Work Statement: The goal of this project is to formulate, analyze and solve mathematical models for crevice corrosion damage evolution. The knowledge gained through mathematical modeling and simulation coupled with an experimental plan of investigation provides insight into the fundamental mechanisms underlying crevice corrosion and means to prevent it, and improve our ability to predict metal component performance assessment and life. This work initiated with FY10 funds and continues with FY11 funds. The models receive input from and validation by laboratory experiments that measure different stages of the corrosion process, such as initiation, propagation, stifling (corrosion slows) and arrest (corrosion stops). Experiments provide direct measurement of corrosion rates, characterization of interface processes, electrochemical tests for dissolution evolution, and supplemental tests to determine properties of solutions and deposits that affect active and passive states. In turn the models identify material parameters, environmental and system variables that need to be measured.

Key objectives are to:

• Advance the understanding of localized corrosion mechanisms • Assist in establishing guidelines for initiation and propagation of the crevice corrosion process • Identify control actions to slow (stifle) and/or stop (arrest) crevice corrosion

Three models (identified as as a1, a2 and a3) are being developed (FY10) to investigate the corrosion in a thin crevice established between a metal surface and the crevice former. In models a1 and a2 the domain outside the crevice is a thin electrolyte film. In model a3 the crevice former is completely immersed in liquid. a Models (FY10)

a1 Model. This initial model focuses on the scenario in which the only reaction is for the anodic dissolution of a pure metal substrate. a2 Model. This model investigates the same geometry as the a1 model. However, reactions for the anodic dissolution of the metal substrate, the hydrolysis of the metal cations, dissociation of water, and cathodic reduction of oxygen, hydrogen ions and water are included. a3 Model. This model investigates the same species and reactions as the a2 model. However, the crevice former is completely immersed in liquid for this case.

b Models (FY11): While the a models focus on pure metal systems, the b models focus on alloys of iron-chromium-nickel-molybdenum, i.e. stainless steels and higher corrosion resistant alloys. Similar reactive, transport and solution methodologies as the a models are used.

The FY11 work builds on and extends FY10 work and comprises the following:

Task 1: Conceptual formulation of an enhanced damage evolution model (b1), including oxygen and multiple ionic species, for an alloy system in a thin electrolyte film environment outside the crevice – to be started July 2011.

Task 2: Conceptual formulation of an enhanced damage evolution model (b2), including oxygen and multiple ionic species, for an alloy system in a fully immersed environment outside the crevice – to be started Sept 2011.

Task 3: Solution of the models will begin after completion of the simplified a2 model. The a models are providing the framework for the solution procedure – to be started in Dec 2011.

Task 4; Comparison with experiments, b model validation and model refinement – to be started in Mar 2012.

Task 5: Validation of model for pure metals in June 2012.

Task 6: Compilation of data for model inputs (continuing).

Task 7: Compilation of experimental results for model inputs and validation (continuing).

Task 8: Technical assessment of findings and recommendations for continued development in Dec 2012.

Product (deliverables): The knowledge gained through mathematical modeling and simulation coupled with an experimental plan of investigation provides insight into the fundamental mechanisms underlying crevice corrosion and means to prevent it, and improve our ability to predict metal component performance assessment and life. Hence, outcomes of the research are:

• Development of mathematical models and computer codes for reliably estimating the spatial and temporal surface morphology of the corrosively damaged metal or alloy/film interface as a function of environmental, chemical, electrochemical and material effects

• Further development of fundamental scientific understanding of crevice corrosion science to assist in establishing guidelines for initiation and propagation of the crevice corrosion process

• Identification of conditions to slow (stifle) and/or control (arrest) crevice corrosion • Development and evaluation of improved corrosion control and prevention strategies • Development of enhanced methods for prediction of damage evolution and risk assessment in different

applications/environments • Preparation of UCC Project presentations for participation in UCC meetings, technical conferences and

corrosion forums. • Project progress reports. • Publications and presentations

Relevance and Cost of Corrosion Relationship: Crevice corrosion is difficult to detect because it develops in narrow gaps formed by bolt heads and lap joints, for example, with a metal surface. Materials (stainless steels, titanium and aluminum) that usually do not corrode under normal circumstances can be damaged in a crevice corrosion environment. Catastrophic structural failure can occur in situations where corrosion is unexpected or undetected. While much progress has been made in understanding crevice corrosion initiation, propagation (damage evolution of the metal surface) is less characterized. Only limited progress has been made for quantitative descriptions of damage evolution (shape and depth of corrosion), and this information is required for enhanced performance assessment, structural analysis and risk management.

Project Title: Unification of Coating Damage Measurements Principle Investigator: H. Castaneda Work Statement: Organic and inorganic coatings have been used predominately as physical barriers in metallic structures against corrosive environments; current DoD metallic infrastructure and assets are in continuous exposure to aggressive conditions. Coating performance is limited by either deterioration or modification of the chemical and physical properties of the polymer. New technologies are in continuous development to quantify in real time the status on the coated metallic structures. One of the key aspects to extend the reliability and life of such assets is the methods and technologies to measure and characterize the performance and degradation of the coating and the interface metal/coating in real time. Different technologies quantify the aggressive species entering the coating/steel system by considering; the homogeneous or heterogeneous nature of the transport phenomena influencing the behavior of the polymer and metal performance, spatial and temporal status of the material guide to the quantification of the degradation and the performance of the coating, and corrosion damage of the metallic structure. The objective is to develop the integration of the cumulative coating performance assessment with different and reliable monitoring technologies in real time. These measurements will be expressed in simple mathematical functions using the relationship between the measured environmental parameters, the damage and performance of each of the elements of the electrolyte/coating/metallic system. Electrochemical Impedance spectroscopy (EIS) combined with Fluorescence emission response will be used to monitor the physical/chemical variables affecting the performance of the layers and interfaces of the coating system, such as electrolyte/coating and coating/metal. These layers/interfaces control the failure modes, such as blister formation, water permeation, swelling, loss of adhesion, delamination and corrosion. The work and findings are aimed at proof of concept to establish the foundation for quantification of damage function evolution for coating/metal system and basic principles for accelerating testing. A combination of two real time monitoring experimental techniques and simple mathematical modeling work will be undertaken. The effort is organized as follows: Task 1: Conceptual design of a compatible cell for impedance and florescence techniques for different model

coating layers and interfaces Task 2: Laboratory experiments, analysis and characterization of transport mechanisms for different ionic

species Task 3: Compilation of transport mechanisms by speciation in model coating per layer Task 4: Gather and analyze speciation for different mechanisms in different thicknesses in coating model

system Task 5: Conceptual functional expressions for different species in different layers, extent and evolution of

damage, and environments during exposures Task 6: Validate the functional expressions with experimental techniques for prediction of damage and

performance time. Product (deliverables):

• Formulation of a simple model for kinetics of performance of a multi-layer, model coating • Compilation of mechanisms and other supporting data for reliability model • Results of laboratory, analysis and characterizations for different layers • Results of mechanisms and kinetics to support accelerated testing • Technical report/peer review publication(s) of findings • Technical assessment of findings and recommendations for continued development • Participation in UCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: These findings are relevant to corrosion management leading to reduced costs and increased reliability in DoD assets. Also, the objective is to create database and techniques for reliability models for lifetime prediction of DoD assets for coating/metal degradation of initiation, activation and propagation (damage evolution of the metal surface) mechanisms. Quantitative descriptions of damage evolution (shape and depth of corrosion) are required for performance assessment, structural analysis and risk management.

Project Title: Investigation of Organic Coating Interaction with Metals and Alloys

Principle Investigator: M. Soucek

Work Statement: Coatings were formulated with specific steel and aluminum substrates in mind. The substrate changes with oxidation of the substrate, and the interface between the oxidized metal and the organic coating changes. In addition, the corrosion blister affects the coating and in particular the coating degradation process. As metal and alloy choice change, so does the interaction with the coating. New alloys or different metal such as magnesium and titanium interact with the organic coatings. There will be two thrusts in this project: 1) preparation of coated samples for exposure (accelerated Ohio State University, OSU, and outdoor University of Hawaii, UH), 2) Evaluation of exposed coatings at University of Akron using both spectroscopic and wet chemistry techniques.

Inorganic/organic corrosion resistant coatings will be prepared for exposure on a variety of metal substrates including typical aluminum and steel substrates as well as magnesium titanium and emerging alloys. These samples will be sent to UH for environmental exposure and OSU for accelerated exposure. The concept is to gain an understanding of how changing the substrate changes the interaction and corrosion protection of the coating. Wet chemistry with respect to extraction of partially degraded polymeric matrix, and metal ions will evaluated via NMR, MS, MS-MS, IR, Raman, GPC, and other techniques as necessary.

The interface between the coating and oxidizing metal substrate will investigated using grazing (x-ray and/or neutron, IR) techniques. Conventional spectroscopy IR, NMR ( liquid and solid state), and MS will be used supplement the grazing techniques and give insight into any change in the bulk properties of the organic coating. Microscopy specifically SEM and TEM will be used in conjunction with AFM and XPS. Cross-sections can be evaluated to ascertain the generation of metal ions in the organic films. Both model samples of silicon wafer with vapour deposited metal of choice, and standard metal coupon samples will be used. The model samples will be exposed with the coupons. The necessity of the model samples is that for the state of the grazing spectroscopy to capture the nano-meso region of the interface, the samples have to be perfectly flat, thus the silicon wafers. The tasks for 2011-2012 are as follows:

Task 1: Second set of coatings Epoxide and sent to University of Hawaii Task 2: Wafers with Epoxide, Polyurea, and Polyurethane coatings with and without non-metallic corrosion

resistant pretreatments will be sent to Hawaii for exposure Task 3: Evaluation of the exposed coatings ( 1st Set) Task 4: Weathering Testing performed at on both panels and coated wafers (UA) Task 5: Spectroscopic investigation of interface of samples (Dhinojwala) Task 6: Begin to construct a unified model.

Product (deliverables):

-­‐ Coatings of non standard metals in comparison with steel and Al samples June 2011 -­‐ 2nd set of coupons sent to University of Hawaii. (June 2011) -­‐ Wafers with Epoxide, Polyurea, and Polyurethane coatings with and without non-metallic corrosion resistant

pretreatments will be sent to Hawaii for exposure (August 2011) -­‐ Build sample holders for Hawaii and weathering of coated, metal sputtered, silicon wafers (Jan 2012) -­‐ Develop sputtering for mixed metal Al/Cu alloys on Silicon Wafers (Jan 2012) -­‐ Develop sputtering for Fe on Silicon Wafers (March 2012) -­‐ Evaluation of the exposed coatings by Neutron experiments, spectroscopy, electrochemical, and coatings

degradation (July 2011-May 2012) -­‐ Accelerated Weathering samples, preparing, evaluation, electrochemical, coating degradation evaluation -­‐ Evaluation of methods for Early detection of corrosion and rapid screening test protocol -­‐ Start Construction of a unified model (May 2012) Linking nano-scale behavior with real-life -­‐ Samples to internal UCC and DOD participants

-­‐ Quarterly reports Relevance and Cost of Corrosion Relationship: The relationship between the pretreatment or organic coating and the substrate is critical for the control of corrosion and for material lifetime prediction. The DOD is moving away from metal pretreatments for its standard metallic alloys, it is important to understand the interaction between the non-metallic pretreatments with both the organic coating and the metal substrate. Since the DOD is moving toward the usage of newer higher performance alloys, there is a need to understand the interaction of the current protective coatings with the presently used and newer alloys.

Project Title: The Effects of Nanomaterials on Corrosion Resistant Coatings

Principle Investigator: M. Soucek

Work Statement: There are a number of nanoparticles and nanotubes that exhibit protection against corrosion. In particular, nanoparticles/tubes with electromagnetic properties have been particularly effective. There unfortunately is a lack of understanding as to the mechanism and, as a consequence, a lack of acceptance. There are three levels of understanding that this project seeks to address: 1) Electrochemical interaction between metal substrate, nanoparticles/tubes, and organic coating; 2) Dispersion of nanomaterials; 3) Effects of application of nanomaterial based coatings. The goal of this project is to use coatings that have been already developed and are of interest to the DOD or currently are specified by the military. Model coatings will be utilized for understanding interactions among various components and the substrates. Exterior weathering will be performed at the University of Hawaii, and EIS and accelerated weathering will be performed at the University of Akron Corrosion Center.

A primary nanomaterial that will be studied is carbon nanotubes. The dispersion of the nanotubes will be evaluated for several commonly used polymeric binders for coatings including epoxides, urethanes, ureas, and acrylics. The effect of application, rheology, and curing conditions on the dispersion of carbon nanotubes will be evaluated by TEM and SEM. The commercially available carbon nanotubes are a mixture of conductive (metallic) and non-conductive tubes. As part of the investigation, model coating with 100% conductive and 100% non-conductive carbon nanotubes will be formulated and cured into the coatings to ascertain whether the corrosion inhibiting effect is derived from the metallic or insulator nanotubes. The electrochemical paradigm considers the interfacial and homogeneous mechanisms (transport phenomena and reaction conversions) occurring within the polymer matrix and at the coating/metallic substrate interface locations. We propose to monitor and quantify the degradation/performance mechanisms of the coating and coating/steel system by considering the deterministic nature of the transport phenomena influencing the behavior of the polymer and metal, correlation of the deterministic mechanisms with the performance of the coating, and corrosion damage of the metallic structure. A variety of metal substrates including typical aluminum and steel substrates as well as magnesium titanium and emerging alloys will be used in the study. These samples will be sent to UH for environmental exposure and OSU for accelerated exposure. The concept is to gain an understanding of how changing the substrate changes the interaction and corrosion protection of the coatings.

Tasks are as follows:

Task 1: The interdisciplinary team will be formed (July 2011) Task 2: Sample prepared for electrochemical mechanistic investigation of coatings (August-September 2011) Task 3: Electrochemical mechanism investigated (September 2011-March 2012) Task 4: Sample preparation for comparison of organic polymeric binders (September 2011-March 2012) Task 5: Evaluate Dispersion, orientation, and location as function of polymeric binder and film formation

conditions/parameters (March-July 2012) Task 6: Send coated coupons to 4 sites at University of Hawaii facility. 1 epoxide series (two substrate Al and

steel); 1 set Waterborne Acrylic and 1 set Polyurethane. (November 2011-May 2012) Task 7: Comparison of Electrochemical corrosion mechanism for polymeric binders and aluminum and steel

substrates (May-December 2012)

Product (deliverables):

Preliminary mechanistic understanding of the role of carbon nanotubes on corrosion resistance of the metal substrate (December 2012)

2) The importance of the role of dispersion or location of the electromagnetic nanomaterials to corrosion performance of the coating (June 2012)

3) Applicability of approach to different commonly used coatings systems (August 2012)

4) How the application of the coating affects the dispersion of the nanomaterials, corrosion inhibition, and longevity of the coating (December 2012)

5) Sampling and sharing of data with UCC and DOD participants 6) Quarterly progress reports

Relevance and Cost of Corrosion Relationship: The fundamental relationship between carbon nanotubes, the polymeric coating binder, and metal substrate is critical for the control of corrosion and formulation carbon nanotubes and other electromagnetic nanomaterials into presently used protective coatings. The DOD has interest is nanomaterial filled coatings for a variety of end-usages from infrastructures in military bases to combat vehicles. These coatings are presently being used and tested as watertower and bridge coatings at DOD facilities. Defining field application parameters for new coating systems is always necessary.

Project Title: Rapid Assessment of Coatings

Principle Investigator: H. Castaneda

Work Statement: Organic and inorganic coatings have been used predominately as physical barriers in metallic structures against corrosive environments. The main purpose of a protective polymer coating is to extend the service life of an uncoated metal. From an engineering standpoint, the performance of the coating is determined by either deterioration or modification of the chemical and physical properties of the polymer in relation to the physical barrier placed between the metallic substrate and the exposed environment. The coating/substrate damage function represents the deterioration of the original physical/chemical properties of the coating when the substrate is exposed to an aggressive environment.

Different technologies characterize the aggressive species entering the coating/steel system by considering the homogeneous or heterogeneous nature of the transport phenomena influencing the behavior of the polymer and metal. Spatial and temporal statuses of the material provide insight for the quantification of the degradation and the performance of the coating. These in turn relate to corrosion damage of the metallic structure.

Accelerated testing has been focused on the failure mode rather than quantifying the failure mechanisms and determining how such mechanism(s) evolve with time. AC impedance has been routinely used to estimate the coating performance using electrochemical principles. One of the advantages of the use of AC impedance is the characterization of different elements of the cell formed with no stress to the coating or polarization of the metal substrate.

In this study, we are proposing to develop the foundation for a more integrated concept, namely developing a performance/damage function for the coating/steel system using the unique capabilities of AC impedance, real time monitoring techniques and chemical speciation in combination with theoretical mechanistic and statistical aspects.

A combination of experimental techniques and mathematical modeling work will be undertaken. The effort is organized as follows:

Task 1: Conceptual formulation of a simplified mechanistic model, transport processes, kinetics and interfacial processes in the “model-ideal” coating/metal system in steady state for each stage (initiation-transition, active)

Task 2: Formulation of damage evolution model, considering three stages in the degradation process, initiation, activation transition and active state

Task 3: Conceptual formulation of damage functions, including water molecules, oxygen and one ionic species in ideal multilayer coating

Task 4: Formulation and development of a simple reliability model

Task 5: Model validation and refinement through comparison with “ideal coating experiments,

Task 6: Conceptual formulation of an enhanced damage evolution model defined in different environments.

Product (deliverables):

• Development of mathematical models and experimental validation for reliably estimating the spatial and temporal degradation of the coating/metal interface as a function of environmental, chemical, electrochemical effects

• Further development of fundamental scientific understanding of degradation/performance of the coating/metal system to assist in establishing guidelines for initiation and propagation of the dissolution process

• Identification of variability of the degradation process for the interface to couple the probabilistic nature • Identification of conditions to mitigate and/or control corrosion degradation either in the coating or at

the interface level • Identification and evaluation of improved corrosion control and prevention strategies • Identification of fundamental scientific understanding of degradation/performance of the coating/metal

system in multiscale systems. • Publications and Presentations • Technical report/publication(s) of findings • Technical assessment of findings and recommendations for continued development • Participation in UCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: The need for and benefits of improved accelerated tests is well recognized. Benefits include more rapid coating development cycles, more reliable evaluation of coating systems for service, and enhanced performance assessment and life prediction. Also, the objective is to contribute to a database and techniques for reliability models for lifetime prediction of DoD operations for coating/metal degradation of initiation, activation and propagation (damage evolution of the metal surface) mechanisms. Quantitative descriptions of damage evolution (shape and depth of corrosion) are required for performance assessment, structural analysis and risk management.

Project Title: Initial Stages of Biofilm Formation & Microbiology Influenced

Principle Investigator: Bi-min Newby

Work Statement: A standardized method for assessing microbiologically influenced corrosion (MIC) is essential for control and mitigation of MIC. MIC is one of the worst forms of corrosion for metals, and it is often most difficult to identify and correct. It is believed that 50% of corrosion failures in pipelines and ~ 20% of the all corrosion on metallic material surfaces are related to MIC. The initial stages of microbial attachment and interaction with metal surfaces serve as a precursor to MIC. This study intends to monitor the initiation and early stages of biofilm formation and MIC and to establish correlations of behaviors with microbial activities by using flow chamber systems. MIC of various bacterial species (representing MIC relevant microbial activities, e.g. nitric acid production, sulfuric acid production, fermentative acid production, denitrification, sulfate reduction, and metal deposition) on aluminum and carbon steel will be employed as the model systems. A focus of the work will be the investigation of carbon steel MIC by a sulfate reducing bacterium (SRB), Desulfovibrio species, under anaerobic conditions. The effort is organized as follows:

Task 1: Design flow chamber systems to allow short term and long term study of biofilm on MIC

Task 2: Design flow chamber systems to allow biofilm development and associated MIC for both aerobic and anaerobic bacterial strains

Task 3: Monitor, in real time, initial stages of biofilm development and MIC on metal surfaces, and assessing products of microbial metabolism (e.g. dissolved Fe(II), sulfide)

Task 4: Examine MIC extents in terms of corrosion rate, metal surface topography, and pit size/depth measurement

Task 5: Correlate biofilm structure (coverage, thickness and spatial distribution) with MIC behaviors

Task 6: Establish a standardized procedure for MIC study using flow chambers

Collaboration with UCC investigators and others are anticipated in several tasks.

Product (deliverables):

• Standardize chamber designs for studying MIC for various bacterial strains under various conditions (e.g. short term, long term, aerobic and anaerobic)

• Correlate biofilm structure and MIC behaviors that will inform modeling and mitigation strategies for control of MIC

• Standardize procedures for evaluating MIC using flow systems • Technical report/publication(s) of findings • Technical assessment of findings and recommendations for continued development • Participation in UCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: Understanding the basic bacteria and metal surface interactions and establishing the relationship between biofilm structure and MIC behaviors are essential for developing better strategies for combating MIC. In addition, systematic evaluations on the effects of initial stages of bacterial biofilm formation and various microbial activities on MIC using flow-through conditions have rarely been reported. The tasks carried out in the project should provide insights for such evaluations and standardize methods for evaluating MIC.

Project Title: Risk Management of MIC

Principle Investigator: J. Senko

Work Statement: The objective is to apply and enhance the risk management of corrodible equipment and structures due to Microbiologically Influenced Corrosion (MIC). Tools and approaches for risk management of corrodible systems will be applied to corrosion mitigation and control strategies to reduce the risks of MIC. The generic risk management methods will be applied to case studies relevant to DoD applications. The processes for microbial growth and survival are defined with spatial and temporal considerations including microbes/species, nutritent, host structure, initiation/growth/sustainment. The system is analyzed to determine points of intersection to disrupt or offset the detrimental effects of MIC. Strategies for disrupting the MIC process are demonstrated in laboratory experiments. An outcome will be a rational, risk management methodology for analysis of MIC risk and mitigation Further, analysis and test methods will provide means to examine effects of materials on MIC (metals, pretreatments, coatings) and effects of chemical treatments on MIC, e.g. inhibitors/biocides, cleaning/rinsing agents.

Task 1: Describe a systematic approach for risk management be applied MIC risks for corrodible equipment and systems.

Task 2: Identify candidate corrodible systems for consideration in consultation with UCC/TCC participants, other DoD contacts and industry/government contacts.

Task 3: Down select application(s) for this effort. Task 4: Develop MIC process flow diagrams with spatial and temporal considerations including microbiological,

corrosion, environmental and electrochemical processes. Task 5: Identify means to disrupt the MIC processes for corrosion control and demonstrate these in laboratory

experiments. Task 6: Identify corrosion risks and mitigation (barriers) to risks. Task 7: Develop procedures to project the evolution of the MIC corrosive environment and the evolution of

corrosion damage. Task 8: Apply the risk management to a case study to determine current status and make projections of future

performance with alternative corrosion control strategies. Collaboration with UCC investigators, TCC representatives, and others is anticipated in these tasks. Product (deliverables):

Description of a risk management approach for MIC of corrodible equipment and systems. MIC process flow diagrams with spatial and temporal considerations Identification of corrosion risks and mitigation (barriers) to risks for selected application(s) Demonstrate means to disrupt the MIC processes through laboratory experiments Procedures to project the evolution of the MIC corrosive environment and the evolution of corrosion damage A case study of risk management for MIC to determine current status and make projections of future performance with alternative corrosion control strategies. Technical report/publication(s) of findings. Technical assessment of findings and recommendations for continued development. Participation in UCC meetings, technical conferences and corrosion forums. Progress reports Relevance and Cost of Corrosion Relationship: MIC is an insidious type of corrosion affecting most underground structures, pipelines, storgae tanks, aircraft integral fuel tanks, etc. Due to its complexity, MIC is usually overlooked in traditional corrosion studies or simplified to the effects of an artificial or simulated electrolyte without consideration of the biological component of the phenomenon. This project aims at developing a more formal risk management approach to dealing with MIC. Developing and implementing an

effective MIC control strategy is hampered by the difficulty in establishing direct cause/effect relationships between microbial activity and observed corrosion. An improved methodology to guide corrosion control strategies will lower the costs of corrosion due to MIC damage and provide a more technically sound rationale for selection and implementation of corrosion mitigation methods.

Project Title: Induced Current Corrosion

Principle Investigator: S. Lillard

Work Statement: Induced alternating current (AC) degradation has become more widely recognized as a threat to the integrity of underground structures and marine structures, e.g. pipelines co-located with high-voltage transmission lines, AC-powered rail transit systems, and structures where there are stray AC currents. High induced AC voltages on the pipelines lead to AC current discharge at coating defects, which can cause severe corrosion even when the cathodic protection criteria is deemed to be satisfied. However, the mechanisms of AC corrosion are still not well understood. Empirical results for factors affecting AC corrosion are in the early stages of development. Mitigation methods are available but the technical basis and validation has significant uncertainty and can be improved.

The objective of this work is to examine the effects of Alternating Current (AC) induced corrosion, AC/DC effects, and interactions with cathodic protection under controlled laboratory conditions. A primary focus is to determine the effects of surface films and corrosion products on metals on the modulation of the AC/DC currents. In particular, the work includes analyses of metal-oxide-metal (MOM) junctions which can have semiconductor properties and nonlinear effects on the currents. Further, the effects of local environment changes, such as pH, on the AC induced corrosion are examined. The relationships among AC/DC polarization, surface films, the aqueous environment and corrosion are to be determined. The initial work is in the context of buried pipelines that are co-located with high-voltage electrical transmission lines, however, the enhanced understanding of these effects are relevant to a broader range of applications.

Task 1-Design, build and validate a laboratory, bench top experiment to expose metal specimen assemblies to controlled levels of induced currents with independent control of AC and DC.

Task 2 – Conduct laboratory bench top experiments to determine Induced AC impacts on corrosion under freely corroding conditions and at a range of cathodic protection levels.

Task 3– Determine the effects of corrosion products and surface films metals on the induced currents/voltages, e.g. measure i-V characteristics of metal/corrosion product/electrolyte systems where the electrolyte is an aqueous solution or soil.

Task 4--Develop a technical basis for AC Induced effects on corrosion and cathodic protection.

Task 5—Recommend guidelines and procedures for measurements of effects and mitigation methods for AC Induced corrosion.

Product (deliverables):

• Design and validate laboratory apparatus for controlled Induced AC exposures • Present a proof of concept, data and analysis for the magnitude and extent of Induced AC on corrosion

and cathodic protection. • Demonstrate the effect Induced AC on corrosion under controlled laboratory conditions. • Report the magnitude of the effect Induced AC on corrosion under controlled laboratory conditions. • Report the effects of corrosion products and surface films on metals on the induced currents/voltages • Present a technical basis for Induced AC effects on corrosion. • Make recommendations on guidelines and procedures for measurements of effects in field tests. • Preparation of UCC Project presentations for participation in UCC meetings, technical conferences and

corrosion forums. • Project progress reports. • Publications and presentations • Technical assessment of findings and recommendations for continued development

Relevance and Cost of Corrosion Relationship: This project is relevant to corrosion management for reduced costs and increased reliability. Stray current corrosion caused by DC currents flowing between metal structures is well recognized and practical methods for measurement and mitigation are well developed. The risk management for AC Induced corrosion is not nearly as robust with respect to recognition of the risk, determination of the severity of risk, and the implementation of control and mitigation plans. In particular, detrimental effects on cathodic protection are not well defined. The findings inform procedures for monitoring and detection of detrimental corrosion effects, maintenance protocols for remediation and mitigation, and methods for corrosion prevention and control.

Project Title: Corrosion Management in Systems Health Monitoring Principle Investigator: J. Payer Work Statement: Systems Health Monitoring (SHM) combines monitoring of the current system status with prediction of future performance and failure states. The ultimate goal of SHM is twofold: facilitate rational decision-making regarding the safety and reliability of a structure and show proper actions (maintenance, repair, or retrofit, etc.) to take when safety or performance concerns arise. This project addresses the incorporation of corrosion management in SHM. An interdisciplinary team will assess the current status of the treatment of corrosion in SHM and undertake initiatives for technological advances. The effort is organized as follows:

Task 1: Describe Corrosion Processes in Fundamentals Relevant to SHM, i.e. translate corrosion science and technology into terms relevant to SHM Task 2: Link Corrosion Damage Patterns to Loss of Function and Serviceability Task 3: Assess Current SHM Technologies with Emphasis on Treatments Relevant to Corrosion Task 3: Assess Current Understanding Computational, Simulation, and Modeling Capabilities for Relevance to Corrosion Task 5: Assess Tools for Linking Corrosion Damage Detection to SHM and Decision-Making Task 6: Assess Asset Management, visualization and GIS Based Inventory-Database systems for Corrosion in SHM

Product (deliverables): • Formation of an interdisciplinary team comprised of subject matter experts from corrosion

science/engineering and other relevant disciplines • Gather and analyze information to support project tasks • Technical report/publication(s) for Tasks 1 and 2 with an overview and illustration by examples • Technical report/publication(s) of findings for Task 3-6 • Technical assessment of findings and recommendations for continued development • Participate in UCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: This project is relevant to corrosion management for reduced costs and increased reliability. Project findings are relevant for enhanced models for corrosion degradation and mitigation. The project is an important step for enhanced, rational decision-making regarding the safety and reliability of equipment and structures, and to show proper actions (maintenance, repair, or retrofit, etc.) to take when safety or performance concerns arise.

Project Title: Crevice Corrosion Damage Evolution Principle Investigator: G. Young, J. Payer Work Statement: Crevice corrosion is one of the most virulent and damaging forms of corrosion. While much progress has been made in understanding crevice corrosion initiation, propagation (damage evolution) has received little attention. Yet quantitative descriptions of damage evolution are precisely what are required for performance assessment and life prediction. Computational modeling of crevice corrosion damage evolution is the core of this project. The models receive input from and validation by laboratory experiments that measure the initiation, propagation, stifling (corrosion slows) and arrest (corrosion stops). Experiments comprise direct measurement of corrosion rates, electrochemical tests for corrosion rate and corrosion cell behavior and supplemental tests to determine properties of solutions and deposits that affect corrosion rate and corrosion control efficacy. Experimental findings and data inform computational modeling. The effort is organized as follows:

Task 1-Orientation of the interdisciplinary team to corrosion, electrochemistry, chemistry and materials science for crevice corrosion processes Task 2-Conceptual formulation of the model for crevice corrosion damage evolution and plan for iterative model development with evolving treatment of more complex systems Task 3-Compilation and analysis of corrosion data and other supporting data needed for modeling Task 4-Gathering and analysis of existing crevice corrosion models and relevant sub-models Task 5-Development and trials with the initial (α) crevice corrosion model for damage evolution Task 6-Experiments to provide model inputs and to validate the model Task 7-Reiterations of model development and evolution to more complex systems

Product (deliverables): • Formation and orientation of the interdisciplinary team • A conceptual framework and formulation of the model for damage evolution • Plans for iterative model development with evolving treatment of more complex systems • Compilation of data for model inputs • Development of crevice corrosion model(s) • Technical report on the testing and validation of initial (α) model • Compilation of experimental results for model inputs and validation • Technical assessment of findings and recommendations for continued development • Participation in UCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: This project is relevant to corrosion management for reduced costs and increased reliability. Enhanced models for corrosion damage evolution are crucial for determination of performance assessment and life prediction. Information for damage evolution (size, shape, depth of corrosion) is required for structural analysis and risk management. The knowledge provides insight into (a) the development and evaluation of improved corrosion control strategies and (b) enhanced methods for prediction of damage evolution and risk assessment.

Project Title: Contrast Corrosion Damage Evolution in Laboratory Tests and Atmospheric Exposures Principle Investigator: J. Payer Work Statement: The need for more reliable and meaningful accelerated tests is well recognized by subject matter experts in corrosion. Further, several of the UCC investigators have active projects with the goal of developing accelerated tests with greater correlation with atmospheric exposure tests and service performance. This project is designed to supplement and coordinate with these efforts. Laboratory experiments and atmospheric exposures are planned to examine damage evolution on coated aluminum and steel. A focus of the work will be the investigation of the evolution of the corrosive environment during immersion, standard exposure chamber tests and atmospheric corrosion tests. Of primary interest is the behavior at and adjacent to scribes and defects in coatings. A combination of experimental and computational work will be undertaken. The effort is organized as follows:

Task 1: Conceptual formulation of a model for evolution of the corrosive environment at flaws in coated metals, e.g. scribes, pinholes, blisters Task 2: Compilation of corrosion data and other supporting data needed to support the model Task 3: Gather and analyze existing corrosive environment models and relevant sub-models Task 4: Laboratory experiments, analysis and characterization of damage evolution and environments during exposures Task 5: Atmospheric exposures with analysis and characterization of damage evolution and environments during exposures Task 6: Compare and contrast findings in various exposures with respect to insights for improved test protocols and interpretation of results.

Product (deliverables): • Formulation of a model for evolution of corrosive environments at flaws • Compilation of corrosion and other supporting data • Results of laboratory, analysis and characterizations • Results of atmospheric exposure, analysis and characterizations • Technical report/publication(s) of findings • Technical assessment of findings and recommendations for continued development • Participation in UCC meetings, technical conferences and corrosion forums • Quarterly progress reports

Relevance and Cost of Corrosion Relationship: The need for and benefits of improved accelerated tests is well recognized. Benefits include more rapid coating development cycles, more reliable evaluation of coating systems for service, and enhanced performance assessment and life prediction. Several UCC projects are active in this area, and this project is an important supplemental project to these efforts. Significant collaborations and a strong synergy pertain.

Project Title: Initial Stages of Biofilm Formation and Microbiologically Influenced Corrosion

Principle Investigator: Bi-min Newby

Work Statement: The initial stages of microbe attachment and interaction with metal and non-metallic surfaces are important to the development of biofilms and for metals as a precursor to microbiologically influenced corrosion (MIC). Biofilms can degrade performance in flow systems and create conditions that promote degradation of metal and non-metallic substrates. Microbiologically Influenced Corrosion (MIC) is considered as one of the worst forms of corrosion for metals, and it is often most difficult to identify and correct. The objectives of this study are to monitor the initiation and early stages of biofilm formation and MIC and to establish correlations of behavior with various types of microbial activities.

The project team has developed a flow chamber system (see figure below) that allows accurate, reproducible in situ monitoring of biofilm development under well controlled, low-shear flow conditions commonly encountered in natural MIC environments. This flow cell will be used to monitor biofilm formation on metal surfaces and evaluate its influences on corrosion. For initial studies, it is planned to examine aluminum and iron substrates. Six microbial species representing different corrosion-relevant metabolic activities are to be investigated.

Task 1: In situ monitoring of initial stage of biofim development and MIC using thin metal films coated on glass slides-This task is designed to determine whether and how different microbial species interact with and attach on aluminum and iron surfaces. The flow chamber system allows for direct in-situ monitoring of microbial cell attachment, early stage of biofilm formation, and potentially for visualization of the initiation of corrosion. Flow conditions will be varied to obtain the effects of different shear rates. Task 2: Evaluation of longer-term MIC by single-species biofilm-Aluminum or iron stripes will be exposed in the chamber to examine longer-term biofilm development of single species and its influence on the corrosion of the metal stripes. Controls will be included by passing microbe-free aqueous solution through the chambers containing metal stripes. Optical microscopy, fluorescent microscopy and confocal laser scanning microscopy (CLSM) are utilized for examining the 3-D structure and spatial cell distribution of the biofilm. Microbial species are selected to represent MIC relevant microbial activities, e.g. nitric acid production, sulfuric acid production, fermentative acid production, denitrification, sulfate reduction, and metal deposition. Results are correlated to MIC rates with these different types of microbial activities. Task 3: Preliminary study on MIC by multi-species biofilm-With the knowledge of the influence of single-species biofilms on corrosion, preliminary study is undertaken for the development of multi-species biofilms and the effect of the species interactions on MIC of iron. Spatial distribution of different microbial species in the biofilm is examined using fluorescent in situ hybridization (FISH) and CLSM. Product (deliverables):

• Formation of an interdisciplinary team comprised of subject matter experts from chemical and biomolecular engineering and corrosion and reliability engineering

• Validation of the technique for in situ observation of early-stage biofilm formation on metal surfaces and for the ability to visually monitor the progress of corrosion

• Determination of rates of biofilm formation of 6 species and, potentially, the associated initiation of corrosion under different flow conditions

• Demonstrate application of state-of-the-art techniques, e.g. CLSM, for characterization of 3-D structures of single-specie biofilms and for examination of MIC

• Measure 3-D structures of developing and mature biofilms of 3 single species • Demonstrate application of gene probes (e.g. FISH technique) for indentifying spatial distribution of

different microbial groups in multi-species biofilm and application to preliminary results on corrosion and 3-D structures of multi-species biofilm

• Participation in UCC meetings, technical conferences and corrosion forums

• Quarterly progress reports • Technical report/publication(s) for Tasks 1-3 • Technical assessment of findings and recommendations for continued development

Relevance and Cost of Corrosion Relationship: This project is relevant to corrosion management for reduced costs and increased reliability. Biofilms can degrade performance in flow systems and create conditions that promote degradation on metal and non-metallic substrates. Microbiologically Influenced Corrosion (MIC) is considered as one of the worst forms of corrosion for metals, and it is often most difficult to identify and correct. Findings of this work (a) provide techniques for the development and evaluation of treatments to ameliorate biofilm growth and MIC, (b) provide input to the modeling of biofilm growth and MIC and (c) enhance the understanding of these processes.

Project Title: Electromagnetic Radiation Effects on Corrosion

Principle Investigator: J. Payer, N. Ida

Work Statement: As a result of increased impedance to ground, small amounts of corrosion can be debilitating to the performance of antennas. The effect on corrosion on this degradation of performance is less obvious and often hidden. This project focuses on (a) the effects of electromagnetic radiation on corrosion and (b) the effects of corrosion and antenna-to-ground impedance. Materials of interest are aluminum and steel in corrosive marine environments for topside structures, antennas, and exterior cabling. There has been no quantification of the effect of electromagnetic radiation in a highly corrosive maritime environment on antennas and topside structures. Corrosion products between metals have diode characteristics which can affect subsequent corrosion and impact antenna performance through increased impedance to ground. While induced AC effects on corrosion have been studied, the effects of electromagnetic radiation are largely unexplored.

Task 1 – Conduct laboratory bench top experiments as a proof of concept to determine electromagnetic radiation impacts on corrosion beyond the normal corrosion in a maritime environment. Control the electromagnetic environment by using selected frequencies from the spectrum segments from 2 MHz – 5.8 GHz.

Task 2 – Determine the effects of corrosion products between metals on impedance between metal-metal structures, i.e. measure the i-V characteristics of metal/corrosion product/metal junctions.

Task 3—Develop guidelines and procedures for measurements of effects in field tests with controlled electromagnetic radiation environments.

Success Criteria include development of laboratory procedures and experimental apparatus for measurement of electromagnetic radiation effects and measurement of the i-V characteristics of metal/corrosion product /metal junctions.

Product (deliverables):

• Demonstrate the effect electromagnetic radiation on corrosion under controlled laboratory conditions. • Determine the magnitude of the effect electromagnetic radiation on corrosion under controlled

laboratory conditions. • Measure the effects of corrosion and antenna to ground impedance. • Develop guidelines for specimens and procedures for realistic field measurements • Participate in UCC meetings, technical conferences and corrosion forums • Quarterly progress reports • Technical report/publication(s) for Tasks 1-3 • Technical assessment of findings and recommendations for continued development

Relevance and Cost of Corrosion Relationship: This project is relevant to corrosion management for reduced costs and increased reliability. The costs of electromagnetic radiation effects on antenna and structures have not been determined. The corrosion effects of ground degradation, subsequent antenna performance, and communications/intelligence are significant and only recognized anecdotally if at all. However, to our knowledge, there has been no quantitative cost analysis. The work is relevant to shipboard and land-based communication system performance. The findings inform procedures for monitoring and detection of detrimental corrosion effects, maintenance protocols for remediation and mitigation, and methods for corrosion prevention and control.

Project Title: Investigation of Organic Coating Interaction with non-standard Metals or Alloys

Principle Investigator: Bi-min Newby

Work Statement: Coatings are formulated with specific steel and aluminum substrates in mind. The substrate changes with oxidation of the substrate, and the interface between the oxidized metal and the organic coating changes. In addition, the corrosion blister affects the coating and in particular the coating degradation process. As metal and alloy choice change, so does the interaction with the coating. New alloys or different metal such as magnesium and titanium interact with the organic coatings. There will be two thrusts in this project: 1) preparation of coated samples for exposure (accelerated Ohio State University, OSU, and outdoor University of Hawaii, UH), 2) Evaluation of exposed coatings at University of Akron using both spectroscopic and wet chemistry techniques.

Inorganic/organic corrosion resistant coatings will be prepared for exposure on a variety of metal substrates including typical aluminum and steel substrates as well as magnesium titanium and emerging alloys. These samples will be sent to UH for environmental exposure and OSU for accelerated exposure. The concept is to gain an understanding of how changing the substrate changes the interaction and corrosion protection of the coating. Wet chemistry with respect to extraction of partially degraded polymeric matrix, and metal ions will evaluated via NMR, MS, MS-MS, IR, Raman, GPC, and other techniques as necessary.

The interface between the coating and oxidizing metal substrate will investigated using grazing (x-ray and/or neutron, IR) techniques. Conventional spectroscopy IR, NMR ( liquid and solid state), and MS will be used supplement the grazing techniques and give insight into any change in the bulk properties of the organic coating. Microscopy specifically SEM and TEM will be used in conjunction with AFM and XPS. Cross-sections can be evaluated to ascertain the generation of metal ions in the organic films. Both model samples of silicon wafer with vapour deposited metal of choice, and standard metal coupon samples will be used. The model samples will be exposed with the coupons. The necessity of the model samples is that for the state of the grazing spectroscopy to capture the nano-meso region of the interface, the samples have to be perfectly flat, thus the silicon wafers.

Success will be defined as (1) Gaining knowledge on how to formulate corrosion resistant coatings for non-conventional metals/alloys and (2) Connecting the organic coating at the interface as a function of corrosion of the substrate with the bulk coating, and ultimately failure of the systems

Product (deliverables):

• Develop experimental plan for exploratory experiments • Prepare inorganic/organic corrosion resistant coatings for exposure on a variety of metal substrates • Deliver specimens to UH for environmental exposure and OSU for accelerated exposure. • Examination of specimens from environmental exposure • Examination of specimens from for accelerated exposure. • Analyze results with respect to coating/interface/substrate interactions and effects on corrosion

performance • Quarterly progress reports • Technical report on assessment of results and for continued development.

Relevance and Cost of Corrosion Relationship: The findings are relevant to the UCC thrust on correlations among laboratory exposures, atmospheric exposure and service and provide an enhanced technical basis for understanding coating/substrate corrosion performance.

Project Title: Coating-Metal Interaction & Strippable Primer/ Enzyme Strippable Primer

Principle Investigator: M. Soucek

Work Statement: This is an exploratory development project for a new primer technology which will have a vastly smaller environmental footprint in its lifecycle. An enzyme strippable primer has usage both as a tool to investigate corrosion of the substrate, and as a primer which can be easily removed without solvents or abrasive blasting. Lightly cross linked PLAs and PHA based will be utilized. Other polyester monomers will be needed to prepare viable coating formulations with the proper balance of application viscosity and end coating properties. Various esterase type enzymes will be used to diminish the molecular weight and increase the number of acid groups to remove the coating with a gentle alkaline solution. The criteria for success of a new primer technology are: 1) properties similar or better to presently used primer, 2) removal using enzyme followed by a aqueous wash.

Product (deliverables):

• Develop experimental plan for exploratory experiments • Preparation and evaluation of Series I coating formulations • Preparation and evaluation of Series II coating formulations • Quarterly progress reports • Technical report on assessment of results, guidelines for further development and research plan for

continued development. Relevance and Cost of Corrosion Relationship: A removable coating with the pretreatment and substrate intact has major benefits for lower direct costs and reduced time. The benefits of reduced environmental impacts are significant.

Project Title: Friction Stir Welding for Assembly of Aerostructures Principle Investigator: A. Patnaik Work Statement: The invention of Friction Stir Welding (FSW) in 1991 has provided airframers with an alternative to mechanical fastening for airframe assembly. Most highly alloyed, high strength, aluminum alloys are not readily weldable by fusion processes due to problems associated with hot cracking and the formation of undesirable microstructures. The FSW process, because it is performed in the solid state, provides the opportunity to weld these alloys. However, while the process is solid state, it is not low temperature. Peak welding temperatures from 300-600°C may occur. These temperatures can and do cause metallurgical changes in the weld zone and the heat affected zones of aluminum alloy friction stir welds. Because of the high temperatures associated with FSW, it is important to understand the metallurgical reactions that may take place during the process and to understand how these reactions will affect subsequent performance of the welded structure including residual strength, fatigue, and corrosion. In order to obtain the best possible performance from friction stir welded structures, it is critical to make proper choice for alloy, starting temper, weld process parameters, and post weld heat treatment. To demonstrate the criticality of some of these factors we propose the following program of study: Alloy: 7050/6.4 mm thick. Starting temper: T7451 and W Welding parameters: high power/high speed/low energy input. Sufficient weld length to support the evaluations described below in the conditions outlined under Post weld heat treatment. Two post weld heat treatment conditions:

1. T7451→Weld→T6 (24 hours at 121°C) 2. W→Weld→T7 type (121°C for 10 hours +163°C for 3 hours)

Evaluations: 1. Optical metallographic examination of weld nuggets: characterization of grain size and morphology. 2. Transverse tensile strength.

a. 3 replicates per condition with standard strain measurement. b. 1 replicate per condition with full-field strain measurement.

3. Hardness distribution at weld mid-plane (two cross sections per weld). 4. Residual stress by cut compliance (after post weld aging, 2 replicates per condition at ¼ and ¾ weld

position). 5. Corrosion evaluation

a. ASTM G34 for exfoliation susceptibility: 5 replicates. b. ASTM G110 for intergranular corrosion susceptibility: 5 replicates.

6. Breaking load testing: number of specimens and load levels to be negotiated with Alcoa Technical Center (J. Moran at ATC has committed to perform some testing gratis).

7. Alloy 7050 is suggested because (1) it is available in our lab, (2) we have substantial experience friction stir welding it and (3) it or alloys similar to it are of interest for use in friction stir welded aerostructures by the major airframers. Starting tempers of T7451 and W are chosen because (1) T7451 is commonly used in airframe applications requiring a balance among strength, toughness, and SCC resistance while proper welding of W and subsequent post weld heat treatment can provide an optimum distribution of mechanical properties in the weld. Generally 7XXX series alloys must be welded at relatively high speeds in order to maintain reasonable strength levels in the heat affected zones. High speed welding requires high power and the two together normally result in a low energy per unit weld length. However, the welding power must be kept low enough so as not to exceed the incipient melting temperature of the alloy. With regard to the suggested post weld heat treatments, the T6 applied to the weld made in the T7451 temper will stabilize the weld zone properties without adversely affecting the base metal, while the weld made in W temper material can be fully aged to a T7451 condition and achieve nearly base metal strength throughout the weld zone.

With respect to the suggested evaluation methods, transverse tensile testing is a standard method of measuring the joint efficiency as UTS of the joint in transverse tension divided by base metal UTS. Coupling of transverse tensile testing with full field strain measurement via digital image correlation will provide information relating to property distributions in the weld and strain localization during deformation. Midplane hardness traverses serve the same purpose in a more standard format. Residual stresses are of great import due to their effects on fatigue crack initiation and stress corrosion cracking. Measurement by cut compliance provides a through thickness average of the longitudinal stress distribution that has good spatial resolution and accuracy. In addition, the method is simple and robust. Corrosion evaluation by the ASTM test methods cited will illustrate the differences in pitting, intergranular and exfoliation corrosion resistance of the weld zones which result from welding with different initial conditions, welding parameters, and post weld heat treatment. In addition to photographic documentation of the surfaces, cross-sectional metallography will be performed to document the variation in corrosion resistance across the welded region into the base plate. This behavior will then be correlated to the results of the mechanical evaluations listed above. All welding, heat treating, and evaluation (except for breaking load testing to be performed at ATC) will be performed at the University of South Carolina. UVA personnel will be available for consultation regarding interpretation of ASTM G34 and G110 test results. Product (deliverables): The final deliverable will be a report which illustrates the fact that not all friction stir welds are created equal. Substantial effort must be made to optimize for a particular application. Critical issues which must be considered include not just the alloy but the temper and the welding parameters which can be accessed for a given alloy and gage.