Influence of Surface Films and Adsorption of Chloride Ions on SCC of Austenitic Stainless Steels in 0.75M HCl at Room Temperature

Abstract

In situ surface enhanced Raman spectroscopy (SERS) was used to investigate the surface films that form on 304 and 316L stainless steels in a number of acidic solutions that either cause stress corrosion cracking (SCC) at room temperature (O.75M HCl) or do not cause SCC at room temperature (0.75M NaCl (pH3), 0.74M H2SO4, 0.87M HC1O4 and 0.75M HBr). The results indicate the same film forms on the steels in all solutions except 1M NaCl (pH3). Hence, while a specific surface film may be necessary for SCC, it is not sufficient to cause SCC of tensile stressed stainless steels. It was also determined that adsorption of chloride ions on stainless steel in 0.75M HCl does not occur in the range of potentials in which SCC occurs. Hence, the role of chloride in causing SCC of stainless steels in acidic solutions at room temperature is not associated with either the formation of specific surface films or adsorption of chloride ions.