Investigations were carried out on effect of cathodic and anodic polarization and applied tensile stress on time-to-failure of Types 302 and 304 austenitic stainless steels in MgCl2 under conditions leading to a better reproducibility of experimental results than those usually observed using boiling 42 w/o MgCl2 and uniformly stressed test specimens. Instead, boiling 35 w/o MgCl2 and specimens with a narrow part situated below the liquid level were used.
Results show that slight cathodic polarization by an external current stops scc, whereas anodic polarization enhances corrosion. This finding confirms some earlier observations but contradicts another viewpoint concerning the effect of hydride phase formation.
For both Types 302 and 304 steels the effect of stress on time to failure is found to differ considerably from typical plots heretofore reported. At loads higher than the yield strength, susceptibility to scc initially increases with stress and then decreases before finally increasing again. This probably is due to the effect of strain on dislocation arrangements within alloy crystals.
