Corrosion behavior of Ni-base alloys in aqueous HCl solution of pH 2 at high temperature and pressure

The unique properties of supercritical water (SCW) have enabled its application in the destruction of aqueous organic wastes. However, drastic changes in properties of SCW as it approaching the critical point also affect the degradation behavior of constructional alloys. The corrosion behavior of Ni-base alloys was studied at pH 2, water temperature in the range 300–425 °C, and at a constant pressure of 24.1 MPa. Aggressive corrosion is observed at high subcritical temperature and minimal corrosion is observed at supercritical temperature. At subcritical temperatures, selective dissolution of Ni and the oxidation of Cr have been observed, and increasing Cr content improved corrosion resistance.