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) environment, a 15 µm Cr coating was prepared on Alloy 625 by magnetron sputtering, and the effect of oxygen concentration (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 containing 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.