The high-temperature and high-pressure(300 ℃/10 MPa) corrosion electrochemical behavior and oxide film microscopic features of Incoloy 800H alloy aged at 675 ℃ for 0～10 000 h in alkaline environament were investigated systematically. By means of electrochemical test

long-term immersion test

scanning electron microscope/transmission electron microscope observation

Raman spectroscopy/fast Fourier transform analysis and other methods

the electrochemical activity

evolution of oxide film morphology and composition characteristics of the 800H alloy with extension of aging time were systematically studied. The results show that

the value of open circuit potential and self-corrosion potential Ecorr of the 800H alloy in high-temperature and high-pressure water can be slightly increased by aging treatment

but the effect of aging time extension on the electrochemical behavior was not significant. A passive to trans-passive process was depicted. The oxide film of the 800H alloy formed in hightemperature and high-pressure water had a multilayer structure: the most outer layer was the dispersed large particle oxides composed of Fe_2O_3 or NiFe_2O_4; the middle layer was relatively compact small size oxides

mostly NiFe_2O_4 or FeCr_2O_4; while the inner layer was dense and continuous oxides

amorphous or nanocrystalline oxide containing Cr and a small amount of Fe. The 800H alloy has good corrosion resistance and surface stability in alkaline high temperature and high pressure water of 300 ℃/10 MPa.