Stress Corrosion Cracking of Austenitic Stainless Steels Under Potentiostatic Polarization : The effect of the plastic deformation on the electrochemical behavior (2nd report)

The results of stress corrosion cracking test for SUS 27 and SUS 33 under potentiostatic polarization in hot magnesium chloride solution were reported in the previous paper. The effects of the stress or strain and strain rate on the electrochemical behavior were investigated in relation to stress corrosion cracking. The polarized specimen without plastic deformation under the potential range for S. C. C to occur shows originally the passivation property, while the once plastically deformed specimen becomes remarkably activated for anodic dissolution. The activation behavior by plastic deformation is associated with local break down of passivity at slip steps and then selective dissolution at the rougher slip steps. Thus, it is considered that localized anodic path leading to the stress corrosion crack is brought by the continuous forming of slip steps under the condition of relatively unstable passivity. The folding point on stress vs time to failure curve is a critical stress whether the effective slip step as active site can be formed immediately after stressing.