Localized corrosion of magnetite on ferritic–martensitic steels exposed to supercritical water

Magnetite usually forms on ferritic–martensitic (F–M) stainless steels as a protective barrier when the steels are exposed to supercritical water (SCW). However, a novel localized corrosion was observed on magnetite induced by adsorbed Cu2S. The morphology and chemistry of the localized corrosion were studied by means of scanning electron microscopy, focused-ion beam, energy dispersive X-ray spectroscopy, and Auger electron spectroscopy. The mechanism of the development of the localized corrosion is elucidated in this paper. The presence of Cu2S or related species should be eliminated for the applications of F–M stainless steels in SCW environment.