Oxidation-sulfidation attacks on alloy 600 in supercritical water containing organic sulfides

摘要

The corrosion characteristics of alloy 600 in supercritical water containing organic sulfides was investigated after an exposure at 480 degrees C and 25 MPa for 72 h. A duplex-structure corrosion scale was observed, with the outer layer predominantly consisting of NiS. The inner corrosion layer was composed of Cr-rich spinel oxides and the fast channels (resulting from the interconnected sulfidation productions such as NiS and Ni3S2) for outward transport of metal cations. This phenomenon can be attributed to the emulative oxidation-sulfidation of alloy 600 because the supercritical water containing organic sulfides system may become a mixture of dominant SCW and H2S due to the gasification reaction of organic sulfides. The formation and growth processes of corrosion scales was also discussed. (C) 2019 Elsevier B.V. All rights reserved.