交流杂散电流对长输管线钢腐蚀行为的影响

Impacts of AC stray current on the corrosion behavior of pipe steel for long-distance pipeline

采用电化学技术和失重法研究了管线钢在两种碳酸盐溶液中的交流杂散电流腐蚀行为。在稀／浓两种碳酸盐溶液中，电化学实验结果表明：管线钢的极化行为表现为极化曲线发生电流振荡现象，振荡幅度随交流电流密度与直流电流密度的比值增大而增大，在腐蚀电位±100mV附近振荡最为显著。腐蚀失重实验结果表明：当交流杂散电流密度为0～20A／m^2时，发生均匀腐蚀且速率较小；当交流杂散电流密度为20～100A／m^2（浓碳酸盐溶液）或20～200A／m^2（稀碳酸盐溶液）时，发生均匀腐蚀且速率增大；当交流杂散电流密度为200～500A/m^2（浓碳酸盐溶液）或大于500A/m^2（稀碳酸盐溶液）时，发生局部点蚀。交流杂散电流造成的腐蚀量约为相同直流杂散电流造成腐蚀量的1％。

In this paper, electrochemical techniques and weight-loss method are used to identify how AC stray current corrodes pipeline steel in two carbonate solutions （dilute and concentrated）. The result of electrochemical experiment shows that the polarization behavior of pipeline steel is manifested as the current oscillation of polarization curve. Its amplitude increases with the ratio of AC density and DC density, especially near the corrosion potential of ±100 mV. The result by weight-loss method shows that the corrosion occurs equably at low rate when the AC stray current density is 0-20 , but at higher rate when the AC stray current density is 20-100 A/m^2 in thick carbonate solution and 20-200 A/m^2 in dilute carbonate solution; local pitting corrosion occurs when the AC stray current density is 200-500 A/m^2 in concentrated carbonate solution and more than 500 A/m^2 in dilute carbonate solution. The corrosion volume caused by AC stray current is about 1% of the corrosion volume caused by the same DC stray current.