Intergranular Corrosion of a Ferritic Stainless Steel

The chromium‐depletion theory of intergranular corrosion has been confirmed for a ferritic stainless steel. The potential range over which intergranular attack occurs is limited by the passivation potential of the matrix and that of chromium‐free iron. The concentration of chromium in the depleted zone is less than 5% at most grain boundaries and approaches 0% at a few. The width of the depleted zone is less than 1 µm. Under strongly oxidizing conditions another form of intergranular attack occurs in both the sensitized and nonsensitized conditions.