Spot-Welded Specimen Maintained Above the Crevice-Repassivation Potential to Evaluate Stress Corrosion Cracking Susceptibility of Stainless Steels in NaCl Solutions

A test is proposed to evaluate the susceptibility of austenitic stainless steels to SCC, particularly in low-concentration chloride solutions. A spot-welded specimen with both a crevice and residual stresses was immersed in the NaCl solutions, and kept potentiostatically for 72 hours at a potential slightly above the crevice repassivation potential with no additional applied stress. This method was also adopted in the development of an improved SCC resistant type 304 steel. The SCC critical temperature was measured for a group of 52 highly purified steels in which the P, Cu, Mo and Al contents were systematically varied. A 14Cr-16Ni-0.013P-2CU-1A1-(0.3̃1) Mo steel was found to have a high critical temperature of HOC, which is markedly higher than that of the conventional type 304 steel (50C) and therefore, it is a good candidate for industrial applications.