Intergranular Corrosion of Nonsensitized Austenitic Stainless Steels

The effects of alloying additions on the intergranular corrosion of nonsensitized austenitic alloys in boiling nitric acid-dichrornate solutions have been determined. Controlled additions of C, N, O, Mn, S, Si and P to a high purity 14% Cr-14% Ni-bal Fe alloy and subsequent corrosion tests in boiling 5 N HNO₃–0.46 N Cr⁺⁶ solutions have shown that only Si and P promote severe intergranular corrosion susceptibility of nonsensitized alloys. Elimination of Si and P from austenitic alloys of otherwise commercial purity decreases susceptibility to inter-granular attack by a factor of six to eight.