STRESS-CORROSION CRACKING OF AUSTENITIC TYPE-304 STAINLESS-STEEL IN SOLUTIONS OF HYDROCHLORIC-ACID PLUS SODIUM-CHLORIDE AT AMBIENT-TEMPERATURE

Austenitic type 304 (UNS S30400) stainless steel is susceptible to str ess corrosion cracking (SCC) in acidic chloride (Cl-) solutions at amb ient temperature. In this study, a layer of adsorbed product film enri ched in chromium and nickel was found to form on the metal surface in the solutions. This product film had a protective role over the base m etal. The nucleation of stress corrosion cracks was connected with the formation of the film and the buildup of a high local concentration o f Cl-. Observation by scanning electron microscopy and transmission el ectron microscopy showed the propagation of stress corrosion cracks wa s associated with selective corrosion of deformation-induced martensit e. The probable mechanism of transgranular SCC in this system was slip dissolution.