高矿化度介质中J55钢的CO_2腐蚀电化学行为

ELECTROCHEMICAL CORROSION OF J55 STEEL IN HIGH SALINITY CO_2 BRINE

通过动电位极化曲线和电化学阻抗谱(EIS)的测试,研究了高矿化度溶液中矿化度对J55钢CO_2腐蚀电化学行为的影响.结果表明:在高矿化度介质中,J55钢的CO_2腐蚀为阴极控制.随溶液矿化度增大,腐蚀电位正移,腐蚀速率先升高,后降低,当矿化度为62.423 g/L时,腐蚀速率最大.随溶液矿化度增加,J55钢的CO_2腐蚀由电化学步骤控制转变为传质和电化学步骤混合控制,并且矿化度越高,传质控制越明显.J55钢的电化学阻抗谱呈现3个时间常数,即高频容抗弧、低频感抗弧和低频容抗弧.随溶液矿化度增大,电荷传递电阻先减小后增大,在62.423 g/L左右出现极小值.

The potentiodynamic polarization and electrochemical impendence spectroscopy （EIS） techniques were employed to analyze the effect of salinity on electrochemical characteristics of J55 steel in high salinity CO2 brine. The results show that the CO2 corrosion mechanism of J55 steel is cathode control, corrosion rates increase as brine salinity increased from 12.485 to 62.423 g/L, then decreases as the brine salinity increased from 62.423 to 407.997 g/L. With increasing of brine salinity, the corrosion potential shifts positively and the corrosion mechanism changes from electrochemical steps control to mixed mass transfer-electrochemical steps control. The higher the salinity is, the more obvious the mass transfer control will be. The EIS plots present three time constants： capacitance loop in high frequency, inductance and capacitance loops in low frequency. The charge transfer resistance （Rt） decreases with brine salinity up to 62.423 g/L, then increases above 62.423 g/L. There are a minimum of Rt and a maximum of corrosion rates at about 62.423 g/L. KEY WORDS CO2 corrosion, salinity, J55 steel, potentiodynamic polarization, EIS