THE EIS ANALYSIS OF CATHODIC REACTIONS DURING CO2 CORROSION OF N80 STEEL
N80油套管钢CO2腐蚀阴极过程电化学阻抗谱分析

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.