Effect of Chromium Ion from Autoclave Material on Corrosion Behavior of Nickel-Based Alloys in Supercritical Water

Abstract Seven kinds of corrosion tests were carried out on thirteen kinds of nickel-based alloys in subcritical and supercritical water containing 0.01 mol/kg sulfuric acid (H2SO4) and 800 ppm oxygen (O2) using a Ni-44Cr-1Mo autoclave. The obtained corrosion rates were significantly lower than the previous experiments performed under the same conditions using a titanium autoclave. A compact oxide scale was found on the specimens tested in the Ni-44Cr-1Mo autoclave. The chromium-rich oxide layer would originate from the autoclave material and provide a protective function against corrosion. The corrosion retardation phenomenon has been explained by dependencies of chromia (Cr2O3) solubility on the phase state of water and temperature.