Crevice corrosion behaviors of Alloy 690 and 405 stainless steel in chloride solutions with different concentrations of thiosulfate

The crevice corrosion behaviors of Alloy 690 and 405 stainless steel (SS) in chloride (Cl -) solutions with different concentrations of thiosulfate (S2O3 2 -) were investigated using a self-designed electrochemical testing device for crevice corrosion. The increase of concentration ratio of Cl-/S2O3 2 - promotes crevice corrosion of Alloy 690. When crevice corrosion occurs between Alloy 690 and 405 SS, Alloy 690 outside the crevice is used as the cathode for reduction reaction of O 2 , and Alloy 690 inside the crevice is also used as the cathode for hydrogen evolution reaction, both of which jointly promote the anodic dissolu-tion of 405 SS inside the crevice. The crevice corrosion mechanisms of Alloy 690 and 405 SS are also discussed.(c) 2022 Elsevier B.V. All rights reserved.