Effect of Applied Stress on Pitting Corrosion Behavior of Type 304 Stainless Steel in Chloride Environment

Electrochemical measurements with and without stress were conducted to clarify the effect of applied stress on pitting corrosion behavior. In potentiodynamic polarization, the increase of the chloride ion concentration led to the formation of shallower pits. In immersion tests with and without stress in the 4 M MgCl2 solution at pH 5, the pit was formed slightly earlier under applied stress. However, there is no or little effect of stress on the corrosion potential before and after the pit initiation. Furthermore, the pit morphology was changed by applied stress, suggesting applied stress causes the increases in anodic dissolution rate and depassivation pH. No remarkable difference in the anodic dissolution rate was observed in potentiodynamic polarization in 4 M MgCl2 solution at pH 1. Depassivation pHs measured in 4 M MgCl2 solution with and without stress were 1.4 and 1.3 in, respectively. Depassivation pH increased by applied stress.