Effect of oxygen concentration on the corrosion behavior of Cr-coated Ni alloy in supercritical water oxidation environment

To improve the corrosion resistance of component materials in supercritical water oxidation (SCWO) environ-ment, a 15 mu m Cr coating was prepared on Alloy 625 by magnetron sputtering, and the effect of oxygen con-centration (0 M, 0.16 M, and 0.94 M) on the stability of the Cr coating in an SCW environment was investigated. Results show that the stability of the Cr2O3 layer strongly depends on the oxygen concentration in the exposure environment. The protective Cr2O3 layer was transformed to soluble Cr(VI) species and dissolved in SCW con-taining 0.94 M oxygen. Except for Cr2O3, some Fe/Ni containing oxides were also detected. The stability of the Cr coating in SCW with different concentrations of oxygen is discussed.