Study the Influence of DC Stray Current on the Corrosion of X65 Steel Using Electrochemical Method

The Direct Current (DC) which is generated by HVDC ground electrodes can cause severe corrosion of buried pipelines. In order to explore the influence of DC on the corrosion of pipeline, in this paper, firstly, an electrochemical experimental device was built. Then, according to different DC magnitude, the Tafel curves were tested and the corrosion morphology of the specimens were observed. Our results show that with DC current density increasing, firstly, the corrosion rate increases. However, when the DC density reaches 100 A/m2, the corrosion rate decreases because of the formation of the passivation film. And it can be seen by microscope that corrosion product gathers on the surface. With the further increase of the DC density, passivation film dissolves and corrosion product falls off. So corrosion process turns from passivation to action and corrosion rate increases again.