FHWA researchers evaluate the accuracy and reliability of three chloride test kits to determine their performance and accuracy.

On bridges, corrosion is most often caused when steel is exposed to atmospheric conditions, such as salt, moisture, and oxygen. To prevent corrosion on bridges, transportation agencies apply a protective coating to the steel.

Following are detailed descriptions of how the researchers conducted tests using the three kits.
Swab Test
The researcher extracted chloride from a surface area of 150 cm2 (23.25 in2)-a 15-cm-long by 10-cm-wide steel panel-using 15 milliliters, ml (0.51 fluid ounce, fl oz) of de-ionized water for cotton swabbing. To reduce dripping, only one-third of each of the four cotton balls used for swabbing was soaked with de-ionized water. The researcher then absorbed the remaining liquid with an additional cotton ball and used an ion detection strip to measure the concentration of chloride in the extracted solution.

Patch Test
The researcher glued a patch securely onto the steel surface, covering an area of 12.25 cm2 (1.89 in2). The researcher then injected 1.5 ml (0.05 fl oz) of extraction fluid into the patch, then extracted two-thirds of the fluid from the patch and reinjected it to mix the fluid more thoroughly. The researcher then rubbed the patch with a finger for 1 minute to promote chloride solubility. Next the patch was rinsed with an additional 1.5 ml (0.05 fl oz) of extraction fluid. Finally, the researcher combined the two extractions and titrated the resulting 3 ml (0.1 fl oz) of extract with reagents included in the kit.

Sleeve Test
The researcher poured 10 ml (0.34 fl oz) of extraction fluid into a sleeve and then attached the sleeve firmly to the steel panel. The researcher then lifted the free end of the test sleeve and held it upright with one hand to allow the extraction fluid to make contact with the test surface. With the other hand, the researcher massaged the solution through the test sleeve against the steel surface for 2 minutes. The researcher then removed the test sleeve and used an ion detection tube to test the solution for chloride concentration.