The corrosion behavior and mechanism of the buried pipeline interfered by dynamic metro stray current

In this work, simulated experiment was conducted in the laboratory to study the corrosion behavior and the corresponding mechanism under dynamic DC stray current. Dynamic square wave current was used to simulate the dynamic metro stray current exerting on buried pipeline. Effects of dynamic period and amplitude of current density were taken into account in the experiments. The results showed that dynamic period had significant influence on the corrosion rate. When the period was less than 100 seconds, the corrosion was slight and the corrosion rate was only approximately 6% of that caused by the same steady DC current. However, as the period lasted more than 100 seconds, the corrosion rate increased significantly and would be even as high as nearly 80% in case of 4 hours. Besides, the corrosion rate was positively proportional to the amplitude of the current density. The electrochemical impedance spectroscopy (EIS) and the cyclic voltammetry (CV) measurements were conducted to further study the corrosion rates under dynamic stray current with different periods, and it was found that the double electrode layer and the temporary passive state played an important role on the corrosion mechanism.