Effect of Chromate on Stress Corrosion Cracking of Solution Annealed Austenitic Stainless Steel Type 304 in Hydrochloric Acid Solution

Abstract

Stress corrosion cracking (SCC) of austenitic stainless steel type 304 has been investigated as functions of applied stress, chromate concentration and test temperature in 0.82kmol/m³ HCl solution by using a constant load method. It is found that the steady state elongation rate in the SCC-dominated region becomes a useful parameter both for predicting time to failure and for the assessment of SCC susceptibility irrespective of the above factors. However, pitting corrosion takes place over the whole specimen surface at chromate concentrations of 0.09 and 0.1kmol/m³ and leads to fracture (not SCC). In this case, the steady state elongation rate plays no role in predicting time to failure. The critical chromate concentration and critical test temperature are estimated at a constant applied stress of 388MPa. The results obtained, furthermore, support the SCC mechanism already reported, which has been discussed in terms of corrosion current density at crack tips and the length of crack propagation.