Corrosion of Nickel-based Alloy G30 in the Stratum Water Containing H2S/CO2

The influences of temperature and CO₂ pressure on the corrosion of nickel-based alloy G30 in the stratum water containing H₂S/CO₂ were investigated with the aid of electrochemical impedance spectroscopy(EIS), Mott-Schottky analysis and scanning electron microscopy(SEM). The results indicate that alloy G30 is in the passive state in the stratum water, which is related to the formation of the passive film on its surface. This passive film can significantly protect the substrate from further corrosion. And the film protection is enhanced with decreasing temperature and CO₂ pressure. Auger electron spectrometry(AES) and X-ray photoelectron spectrometry(XPS) results reveal that the passive film shows the double-layer structure, i.e. the inner chromium oxide and the outer iron/nickel spinel oxides or hydroxides with Mo oxides dispersing throughout the inner and outer scale.