Intergranular Corrosion of Ferritic Stainless Steels

The susceptibility of both commercial and experimental ferritic stainless steels to intergranular corrosion was investigated. It was found that heating to 1700° F or higher and cooling rapidly sensitized a wide variety of ferritic steels to intergranular corrosion. The effects of Mo, Ni, Cb, and Ti additions to the steels were studied. It was found that Cb and Ti were effective in preventing intergranular corrosion in the Strauss test after high‐temperature heat treatment. However, in highly oxidizing media such as boiling 65% nitric acid, titanium‐containing steels could be sensitized to intergranular corrosion, while the columbium steels resisted intergranular attack even in boiling 65% nitric acid. Controlled potential polarization experiments gave results that agreed with the exposure results.