直流杂散电流对X65钢表面形态及电化学行为的影响

Effects of Direct Stray Current on Surface Morphology and Electrochemical Behavior of X65 Steel

在公用走廊中,高压直流输电线单极运行时产生的杂散电流会对埋地管道造成严重的腐蚀。为了探究直流杂散电流对管道的腐蚀干扰影响,通过三电极体系对不同直流干扰下工作电极的极化曲线、交流阻抗谱进行了测试,并通过共聚焦测量显微镜(SEM)及体式显微镜观察了腐蚀形貌。结果表明:随着外加直流电流密度的增大,工作电极的腐蚀电位和腐蚀电流密度都增大,而当直流电流密度为100 A/m^2时,工作电极表面发生了钝化,腐蚀电位和腐蚀电流密度减小;在外加电流增大的过程中,工作电极的阻抗谱中的感抗弧逐渐消失,变为Warburg阻抗,最后当直流电流密度增加到200 A/m^2时,阻抗谱只出现单一容抗弧;在直流电流密度增大过程中,工作电极表面反应电阻不断减小,在点100 A/m^2处略有增大。

In order to explore the interference effect of direct stray current on the corrosion of pipeline,three electrodes system was built to test polarization curves and electrochemical AC impedance spectra(EIS) of working electrode under various DC conditions,and the morphology of corrosion surface was observed by confocal microscope and stereoscopic microscopes.Results showed that with direct stray current density increasing,the corrosion potential and corrosion current density increased.However,when the DC density reached to 100A/m^2,working electrode was passivated,and the corrosion potential and corrosion rate declined.With applied current density increasing,the inductance loop disappeared gradually and turned into Warburg impedance.When DC current density reached to200 A/m^2,EIS of working electrode presented a single capacitive impedance loop.Furthermore,during the process of DC current density increasing,surface reaction impedance of working electrode decreased,while at 100 A/m^2 it increased slighlly.