Electrochemical Corrosion Study of Buried Pipeline Steel X20 Affected by Stray Current

Abstract

With the continuous development of urban city, more and more subway lines are applied in the urban rail transit systems. During the daily operation of metro, the insulation performance between running rails and earth is gradually decreased. Thus, the stray current is generated at where the current flows out of the running rail. Stray current leakage and the corrosion caused by it are not negligible negative effects. Stray current corrosion will cause severe electrochemical corrosion to the metallic structures in and around the subway system, such as buried pipelines, running rails and concrete reinforcement etc. In view of the current situation of buried pipelines being affected by stray current corrosion, this paper starts with the stray current corrosion experiment of X20 pipeline steel. The experimental system was built up to simulate the stray current corrosion on the buried metallic pipeline. Electrochemical measurements including Tafel method and electrochemical impedance spectrum (EIS) were conducted in this study. Based on the measurement results and microscope morphology, the electrochemical corrosion process of X20 steel was discussed in detail Then the equivalent circuit model of the corrosion system was fitted and analyzed. It was found that the Nyquist plot of X20 corrosion system shows the characteristics of double capacitive reactance arc, and the corrosion system can be equivalent to a Rs(CPEporeRpore)(CPEdlRct) model. Finally, the stray current corrosion in the subway was introduced with engineering background, in which more influencing factors including microorganism, tube pressure, pH and water content value of soil, are pointed out for future research.