Correlation between non‐metallic inclusions and localized corrosion of a low‐nickel stainless steel with cerium treatment

The localized corrosion induced by different kinds of inclusions in a low-nickel stainless steel was studied through immersion tests and first-principles calculations. The galvanic corrosion between the steel matrix and different kinds of inclusions occurred in the corrosive environment due to the difference in the electron work function of the steel matrix and inclusions. The electron work function of MnS, CeS and Ce-O-S was smaller than that of the steel matrix, thus, these inclusions first dissolved as the anode. However, the electron work function of cerium-containing oxides was bigger than that of the steel matrix, and the steel matrix dissolved prior to cerium-containing oxides. The order of the volume expansion rate of pits induced by inclusions was CeS > Si-Mn(-Al)-O > MnS > Ce-C-O-S > Ce-Si-Mn(-Al)-O> Ce-O-S. For cerium-containing inclusions, the electron work function of inclusions increased with the increase of the O/Ce ratio and the S/Ce ratio of inclusions. The order of the electron work function of cerium-containing inclusions was cerium oxides > cerium sulfides > cerium oxysulfide. This article is protected by copyright. All rights reserved.