Effects of different inorganic anions on equipment material corrosion behaviour in subcritical water oxidation

摘要

In this work, possible corrosion mechanisms of Fe- and Ni-based alloys are discussed which are protected by Cr2O3, NiO and MoO2 surface layers. But chloride ions can dissolve these oxide films and there is a strong synergistic effect between hydronium ions and oxygen, leading to severe local alloy corrosion. On the other hand, titanium and Zr-3 alloys show good corrosion resistance in acidic oxidising subcritical water containing different inorganic salts. A double-layer oxide film (TiO and TiO2) is formed on the surface of TA2 and TA9 alloys, while a triple oxide layer (TiO, Ti2O3 and TiO2) is formed on TA10 surfaces in such aqueous solutions containing chloride and sulphate ions. In addition to the two oxide layers, Ti-3(PO4)(4) deposits are also formed on the surface of TA2 and TA9 alloys when the subcritical water contains phosphates. Moreover, (TiO)(2)P2O7 deposits form besides Ti-3(PO4)(4) layers on the surface when the TA10 alloy is oxidised under the latter conditions.