On the interference mechanism of stray current generated by DC tram on pipeline corrosion

The stray current from the DC-electrified traction system can affect the pipeline-to-soil potential and can cause corrosion on the buried pipeline, which will bring about economic losses and even threaten personal safety. Thus, it is necessary to study the stray current generated by the rail potential and its impacts on pipeline corrosion. For this purpose, an analysis approach, in which the theoretical method is used in combination with the finite element model and experimental analysis, is presented. The dynamic distribution equations of the rail potential and the stray current are deduced by using a mathematical model. A finite element model based on the theoretical equations is established to calculate the pipeline-to-soil potential under the interference of the stray current from the running rails. Finally, the obtained pipeline-to-soil potential is used as voltage interference to develop an electrochemical experiment and the variation laws of the electrochemical impedance spectroscopy of the pipeline metal are studied by using this experiment. The theoretical results show that the stray current is proportional to the rail potential. The pipeline-to-soil potential under the interference of different stray current can be expressed as a sine function according to the fitted results of the finite element analysis. And the coefficients of the function are determined by the relative position of the pipeline and the running rails. Meanwhile, the coefficients of the function (amplitude, frequency, and offset) have different influence on the EIS of the pipeline metal.