Metallographic and fractographic studies are useful and sometimes indispensable tools for the analysis of failure of steel products in sour oil and gas environments containing appreciable quantities of hydrogen sulfide.1,2 Products that fail in sour environments, however, are often covered with a tenacious iron sulfide film that obscures features of fractographic interest such as inclusions, fracture mode, etc. This note describes the use of an inhibited hydrochloric acid pickling technique that removes corrosion debris (oxides as well as sulfides) while maintaining fracture surface integrity; this technique also allows meaningful evaluations to be made at relatively high magnifications.
The stock pickling solution used was concentrated hydrochloric acid (37.5% HCl) to which 10 g/liter 1,3-Di-n-butyl-2 thiourea (DBT) had been added. The DBT was obtained from Eastman Organic Chemicals. Immediately prior to use, the stock solution was diluted (50/50) with distilled water, and the specimen was immersed and ultrasonically agitated for 30...
