Measurement of Chloride Contamination on Stainless Steel Surface

Chloride trace contamination on stainless steel surface can initialize localized corrosion especially at high temperature. Polluted air, residue of consumable materials, and bead of perspiration can chloride contamination on the structural materials. An ex-situ method was developed for determining 0.5-10 µg/cm2 chloride contamination on steel coupons.

Chloride can be removed quantitatively from the steel surface by pyrolysis in the presence of a low amount of water steam above 900 °C. It can be collected in basic solution and measured by ion chromatography.  A small, electrically heated quartz tube furnace was constructed for annealing the samples with 10 cm2 surface. High purity argon carrier gas was flown through a water-filled gas-washer, the furnace and a thin collector gas-washer filled with 20 mL 1M Suprapur ammonia solution successively. Flow rate and heating program were optimized. The collector vessel was cooled by ice. Yield of the procedure was determined for each sample by radiotracer method, using 36Cl and liquid scintillation measurement.  Collector solution can be analysed directly by ion chromatography (IC).

The method was calibrated and tested by samples with known surface chloride concentration. Yield of chloride transfer from the steel surface to the solution was 75-99%. By dropping 36Cl containing tracer solution to the sample, the yield can be measured and taken into account. Detection limit of the method is 0.3 µg/cm2.

 

Contact
Zsolt KERNER, MTA Center for Energy Research
zsolt.kerner@energia.mta.hu