Electrochemical Characteristics of Passive Films on Surface of Nicke-based Alloy 825 in Corrosion Environment Containing H2S and CO2
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Graphical Abstract
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Abstract
The passive films on the surface of nickel-based alloy 825 were corroded in the simulated corrosion environment of high temperature and high pressure gas field with H2S and CO2. The effects of temperature and partial pressure ratio of H2S to CO2 on the electrochemical behaviors of passive films were studied by testing polarization curves, electrochemical impedance spectroscopy (EIS) and Mott-Schottky curve (M-S curve). The results show that temperature and partial pressure ratio of H2S to CO2 exhibited the same effect rules. When the temperature rose or the partial pressure ratio of H2S to CO2 increased, the values of double layer capacitance, passive film capacitance and current carrier density increased, but the charge transfer resistance and the passive film resistance reduced, which indicated that the increase of temperature and partial pressure ratio of H2S to CO2 would increase the defects of passive films, and decrease the density and thickness of passive films, making the protection of passive films reduce.
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