Pit initiation on sensitized Type 304 stainless steel under applied stress: Correlation of stress, Cr-depletion, and inclusion dissolution

The effects of applied stress on the pitting of sensitized Type 304 stainless steel were investigated in 4 M MgCl2 immersion test. Regardless of whether stress was applied, pitting was initiated at inclusions at sensitized grain boundaries. In the absence of applied stress, the occurrence of pitting decreased when the area exposed to the solution decreased, and not all the inclusions acted as initiation sites. However, pitting was observed independent of the exposed area under applied stress. The dissolution rates of MnS inclusions and sensitized grain boundaries were accelerated by applied stress.