X65管线钢电化学充氢后在土壤中腐蚀行为

针对油气管道长距离输送所产生土壤质地差异大的工况条件,因氢引起的管道腐蚀问题越来越被人们所关注.基于极化曲线法和电化学阻抗谱法研究了充氢的X65管线钢在格尔木、大港站、大庆站、拉萨站4种模拟土壤溶液中的电化学腐蚀行为.试验结果表明:在同一种土壤溶液中,X65管线钢的开路电位随着充氢时间的增加逐渐降低.不同充氢条件下的X65管线钢在格尔木、大港站、大庆站、拉萨站4种模拟土壤溶液中的极化曲线都只表现出活化溶解状态,而未出现活化-钝化转变区,腐蚀电流密度越来越小,腐蚀速率越来越慢.对EIS进行拟合得出电荷转移电阻R_ct随充氢时间t变化规律,R_ct在4种土壤溶液中大小依次为格尔木<大港站<大庆站<拉萨站,与极化曲线的分析结果一致.

Corrosion Behaviors of X65 Pipeline Steel After Hydrogen Charging in Soil Solutions

In view of the complexity in soil environment caused by long distance transportation of oil and gas pipelines, corrosion problem from hydrogen has received increasing attention. The corrosion behaviors of X65 pipeline steel after electrochemical hydrogen charging with different times in four simulated soil solutions ( in Geermu, Dagang, Daqing, and Lasa ) were investigated using the polarization test and electrochemical impedance spectroscopy ( EIS) measurement. Results show that the open circuit potential ( OCP) of X65 decreases with prolonging charging time in a type of solution. The polarization curves in the four solutions show that X65 with different charging times presents similar electrochemical behavior, which is active in both the anode and the cathode. The smaller the corrosion current density is, the slower corrosion rate is. EIS spectra indicates that the ranking of charge transfer resistance from the biggest is Geermu, Dagang, Daqing and Lasa. It is consistent with the analysis results of polarization curves.