Localized corrosion of 304 stainless steel triggered by embedded MnS

The present work investigated the localized corrosion of 304 stainless steel triggered by MnS in 3.5 wt% NaCl solution via multi-analytical approaches including in-situ and ex-situ techniques. The results suggested that the dissolution of MnS starts from boundary areas and directly releases elemental sulfur. The reoccurrence and disappearance of elemental sulfur during MnS dissolution indicated that sulfur was continuously consumed and converted. Copper-containing compounds were found deposited on residual MnS in the corrosion pit, whilst a thin Cr2O3 film covered the pit and thickened over time. Based on the evidence obtained, a more comprehensive MnS-induced localized corrosion mechanism was proposed.