Crevice corrosion behavior of Alloy 690 in high-temperature water

Characterizations of oxide films formed on Alloy 690 during crevice corrosion in 290 °C pure water were investigated. It was found that different hydrochemistry conditions and potential drop affected the development of oxide films within the crevice. The thick oxide film formed at crevice mouth mainly consisted of compact NiO and NiFe2O4 due to the precipitation of Ni2+ and Fe2+, while the thin oxide film formed within the crevice mainly consisted of an outer layer of Cr(OH)3 and (Fe, Ni)Cr2O4, and a continuous inner layer of Cr2O3, which was attributed to the hydrolysis of Cr3+ and decreased the pH value of the crevice solution. Possible mechanisms of crevice corrosion and growth of the oxide films at different sites along the crevice in high-temperature water are discussed. •The crevice affects the development of oxide films within the crevice.•Hydrochemistry conditions within the crevice are strongly affected by crevice.•The Cr3+ hydrolysis results in formation of Cr-rich oxides within the crevice.•The oxide film at crevice mouth is thick, while it is thin within the crevice.