Sulfide inclusions pitting initiation role

Sulfide inclusions play a major role in pitting initiation on iron alloys, among them stainless steels. It is worth drawing attention to some of their physicochemical and metallurgical properties. 

Besides their possible role in pit initiation (see earlier), the dissolution of the MnS inclusions can generate thiosulfates [47, 67] or more likely sulfide [51, 52] ions, which are known to favor passivity breakdown. Indeed, Crolet et al. [54] observed higher depassivation pH on stainless steels with high sulfur content. According to Brossia and Kelly, the initiation involves a critical [Cl ]/[HS ] ratio. This efiect of MnS is unlikely in modem stainless alloys with very low sulfur contents. 

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