N80油套管钢CO_2腐蚀阴极过程电化学阻抗谱分析

THE EIS ANALYSIS OF CATHODIC REACTIONS DURING CO_2 CORROSION OF N80 STEEL

利用电化学阻抗(EIS)技术研究了N80钢在不同介质条件下CO2腐蚀过程中可能存在的阴极反应及其反应速度.结果表明,N80钢在CO2腐蚀环境下存在H+和H2O以及H2CO3,HCO3-的还原反应,但在不同条件下各个还原反应的速度并不相同.在酸性的饱和CO2溶液中,H+的还原控制着阴极反应速度, HCO3-和H2CO3的还原反应速度较小;在中性的饱和CO2溶液中,阴极过程以HCO3-和H2CO3的还原为主,H+的还原反应速度比较微弱;在碱性的NaHCO3溶液通入CO2后,HCO3-的还原控制着阴极反应速度.在以上条件下, H2O的还原速度比较微弱,还不会对阴极交换电流产生影响.

The electrochemical impedance spectroscopy (EIS) was used to analyze the possible cathodic reactions and reaction rate during CO2 corrosion of steel N80 in various electrolytes. The results demonstrate that H+, H2O, H2CO3 and HCO3- all could be reduced. But the reduction rate is different in various electrolytes. In acidic electrolyte saturated with CO2, the reduction rate of H+ is high and controlls cathodic reaction rate, and the reduction rates of H2CO3 and HCO3- are slow. In litmusless solution saturated with CO2, reduction of H2CO3 and HCO3- become the most important cathodic reaction and the reduction rate of H+ is slow. In NaHCO3 alkalic solution saturated with CO2, only the reduction of HCO3- is the dominant cathodic reaction. In all above-mentioned solutions, the reduction rate of H2O is low and could not influence cathodic exchange current density.