Effects of thiosulfate and dissolved oxygen on crevice corrosion of Alloy 690 in high-temperature chloride solution

Abstract

The crevice corrosion behavior of Alloy 690 was investigated in high-temperature chloride solution containing different concentrations of thiosulfate (S2O32−) and dissolved oxygen (DO). The S2O32− inhibited corrosion of Alloy 690 through consuming oxygen in aerated chloride solution. In deaerated chloride solution, the S2O32− was reduced to S° and S2− and subsequently incorporated into the oxide films, which promoted the pitting corrosion at locations of both TiN inclusions and matrix inside the crevice during the crevice corrosion as well as influenced the composition and thickness of the oxide films. The effect mechanisms of S2O32− and DO on crevice corrosion in high-temperature chloride solution are discussed.