new methods for testing and extraction of soluble salts

New Methods for Testing and Extraction of Soluble Salts Presented by: Dr. Lisa D. Detter-Hoskin, Principal Research Scientist Georgia Tech Research Institute

Introduction• This webinar will describe the most

commonly used field methods for the retrieval and analysis of soluble salts on steel and other nonporous substrates.

SSPC Guide 15• A guide that describes the most

commonly used field methods for extraction and analysis of soluble salts

• Recently revised– Expected to be published in July 2013

Field Methods for Measuring Soluble Salts by Conductivity• Fully Automated Conductivity Measurement

– Soluble Salt Meter– Surface Salinity Meter– Continuous Flow Extraction Fiber Strip

• Multi-Step Conductivity Measurement – Surface Swab or Wash/Probe Type Conductivity

Meter Technique– Adhesively Bonded Latex Patch or Cell/Probe Type

Conductivity Meter Technique– Saturated Special Filter Paper/Concentric Ring

Conductivity Meter Technique

Fully Automated Conductivity Measurement

• Direct real-time automated systems• Measures solution salinity from

conductance• Hand-held and portable• Self calibrating and paperless

Soluble Salt Meter

Continuous Flow Extraction Fiber Strip

Advantages• Some sensors will attach magnetically to some metals• Methods are real time• All critical steps are automated and pre-measured• Reduced setup• Testing can be performed on vertical, horizontal and

overhead surfaces• Methods are paperless; digital output• Reduction in consumables and no hazardous materials

required• Readings may be recorded• Sensor test area is standardized and cannot be

manipulated

Limitations• Meters may not conform to curved and

irregular surfaces• Sensors will not adhere to a surface that

is not magnetic• Measures conductivity of total soluble

salts rather than a specific ion• Fully automated conductivity

measurement techniques must be purchased as systems and are not interchangeable

Surface Swab or Wash/Probe Type Conductivity Meter Technique

Advantages• The swabbing retrieval method provides a

means for acquiring samples of salt from steel or other non-porous surfaces using readily available materials

• Retrievals can be conducted on a range of surfaces without regard to surface irregularities or condition

• The swabbing method can be used on large areas to indicate general surface contamination by salts

• The extractions also provide sufficient sample size for several analyses to be performed for different ions

Limitations• Swabbing methods are difficult to

perform in an overhead or vertical position

• Swabbing is not well suited for measuring salt levels of small, localized contamination such as craters or pits

• There is a risk of contamination of a sample by the operator if gloves or any other equipment used for these procedures become damaged

Adhesively Bonded Latex Patch or Cell/Probe-Type Conductivity Meter Technique

Advantages• Cells can conform to curved and irregular

surfaces• Cells such as these are commercially

available in a variety of sizes• If reagent water has been used as the

extraction liquid, conductivity can be determined using commercially available conductivity meters

Limitations• The adhesively attached cells only

accommodate a small amount of extraction liquid

• No in-line determination of conductivity can be performed with these cells

Limitations• The cell may not adhere well to heavily

rusted surfaces, but it may adhere to abrasive blast cleaned surfaces so well as to cause difficulty in removing the patch

• The cell may leak through the hole introduced by the syringe

• The cells are consumable and can be used only once

• The patch cell will add background conductivity

Limitations• Dilution of extraction liquid introduces

greater error in final result• No standard procedure for the intensity of

rubbing, thus making the result subject to operator

• Flexible patches can be stretched to 10% more than their original intended footprint influencing the final result

• When acidic extraction solutions are used, patch cell is not suitable for conductivity measurement

Advantages• Suitable for a wide range of shapes,

orientations, surface and finishes• Battery operated and portable

Limitations• No in-line determination of

conductivity can be performed with this unit

• Water may be lost from the filter paper introducing error

• The filter paper is a consumable and can be used only to extract salts

• Background correction for the blank filter paper must be manually performed

Field Methods Measuring Specific Ions• Chloride Ion paper Strip Test of Swab/Wash or

Latex Patch/Cell Extracts• Chloride Ion Detection Tube Test of

Swab/Wash or Latex Patch/Cell Extracts• Ferrous Ion Paper Strip Test of Swab/Wash or

Latex Patch/Cell Extracts• Field Drop Titration for Chloride of

Swab/Wash or Latex Patch/Cell Extracts• Latex Sleeve Methodology• Field Detection Sulfate Ion by Visual Turbidity• Qualitative Field Detection of Ferrous Ions

Chloride Ion Paper Strip Test of Swab/Wash or Latex Patch/Cell Extracts

• Chloride ion paper test strips are utilized to determine chloride ion concentrations of swab- or patch cell-extracted solutions

Chloride Ion Paper Strip Test of Swab/Wash or Latex Patch/Cell Extracts

Chloride Ion Detection Tube Test of Swab/Wash or Latex Patch/Cell Extracts

• Sealed vacuum tubes are utilized to determine chloride ion concentrations of swab- or patch cell-extracted solutions

Ferrous Ion Paper Strip Test or Swab/Wash or Latex Patch/Cell Extracts• Ferrous ion paper test strips are

utilized to determine ferrous ion concentrations of swab- or patch cell-extracted solutions

Field Drop Titration for Chloride of Swab/Wash or Latex Patch/Cell Extracts

• Test kit is used to analyze the solution collected from the surface using swab or patch cell extraction methods


• The chart below is used to determine the concentration of chloride ion in the sample

No. of Drops From Bottle 4 Concentration of Chloride Ion

1 Less than 2μg/cm2

2 2-4μg/cm2

3 4-6μg/cm2

4 8-10μg/cm2

Latex Sleeve Methodology• This method uses a small flexible

chloride-free latex sleeve with a self-contained adhesive edge. A proprietary solution is dosed into the sleeve, and the sleeve is attached to the structure being tested, forming a cavity. The solution is massaged against the surface being tested for a specified period of time and is then removed. The sleeve then is removed and extracted solution tested for levels of chlorides.

Latex Sleeve Methodology

Advantages• This method is very simple to

perform, as all components are pre-measured

• The adhesive sleeve can conform to curved and irregular surfaces. Tests can be performed on vertical, horizontal, and overhead surfaces

• For extremely rough or pitted surfaces, the seal ring may be doubled, thereby allowing testing to be performed

Advantages• The kit form of this method provides a

pre-measured volume of extraction solution and a fixed area of the sleeve opening.

• All components are one-time usage, eliminating cross contamination from test to test

• In hot weather or on hot surfaces, the encapsulated extract solution will not evaporate

Advantages• The extractions also provide

sufficient sample size for analyses to be performed for different ions

• Acidic extraction liquids normally provide improved extraction efficiency compared to reagent water

Limitations• The adhesive sleeve may not adhere

well to rusted surfaces, but may adhere so well to clean or grit blasted surfaces that it is difficult to remove the adhesive sleeve from the surface

• No in-line conductivity can be performed with the sleeves

• The sleeves are consumable and can be used only once

Field Detection Sulfate Ion by Visual Turbidity

• Works on the principle that if sulfate is present in the extracted salt solution, it becomes turbid (cloudy) when barium chloride is added

Qualitative Field Detection of Ferrous Ions

• Blotting paper is treated with potassium ferricyanide solution. The blotting paper is moistened and placed in contact with the steel surface to be tested. On contact with ferrous ions, the paper shows blue spots

Summary• This webinar described several ways

to test for soluble salts on a surface. The technique selected is based on whether you want to know both the quantity and the type of soluble salt that is on the surface or, whether you just want to know if soluble salts are present.

Questions?