Crevice corrosion behavior of Alloy 690 in high-temperature water

Abstract 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 NiFe 2 O 4 due to the precipitation of Ni 2+ and Fe 2+ , while the thin oxide film formed within the crevice mainly consisted of an outer layer of Cr(OH) 3 and (Fe, Ni)Cr 2 O 4 , and a continuous inner layer of Cr 2 O 3 , which was attributed to the hydrolysis of Cr 3+ 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.