H2S/CO2腐蚀环境中镍基合金825表面钝化膜的电化学特性

摘要

在模拟高温高压H2S/CO2气田腐蚀环境中对镍基合金825表面钝化膜进行腐蚀试验,利用电化学方法测量其极化曲线、电化学阻抗谱(EIS)和Mott-Schottky曲线(M-S曲线),研究了温度和H2 S/CO2分压比对其表面钝化膜电化学特性的影响.结果表明:温度和H2S/CO2分压比对镍基合金825表面钝化膜的电化学行为影响规律相同,温度升高或H2S/CO2分压比增大时,双电层电容和钝化膜电容均增大,电荷转移电阻和钝化膜电阻减小,载流子浓度增大,说明温度升高和H2S/CO2分压比增大时,钝化膜的致密性降低,容易遭到破坏,厚度减薄,对基体的保护性降低.%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 H2 S 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 H2 S to CO2 exhibited the same effect rules.When the temperature rose or the partial pressure ratio of H2 S 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 H2 S 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.