Corrosion characteristics and mechanisms of typical iron/nickel-based alloys in reductive supercritical water environments containing sulfides

Abstract

The corrosion characteristics of stainless steel 316 and typical nickel-based alloys in supercritical water containing sulfides were investigated by a series of detection methods. Breakaway corrosion occurred on Incoloy 825 and Inconel 600 due to sulfide-formed tunnels or enriched microlayers in the inner layer of corrosion scales. In supercritical water containing sulfides, we find that the alloys with higher chromium and iron contents exhibited superior corrosion resistance than the nickel-rich alloys, which is further confirmed by an analysis of the thermodynamics and the effects of temperature and alloying elements. The corrosion mechanism of iron/nickel-based alloys in reductive supercritical water systems containing sulfides was proposed, especially the related breakaway corrosion mechanism and the effects of temperature and alloying elements. Additionally, prediction models of corrosion products are established to guide material selection.