Effect of OVPD Operation on Stray‐Current Corrosion of U75V Rail Steel in Metro Systems

ABSTRACT

In DC metro traction power systems, stray currents at weak rail insulation regions can induce electrochemical corrosion. Over‐voltage protection devices (OVPD) regulate rail potential and modify stray current characteristics; however, their effects on corrosion remain unclear. Based on measured data, a current field model considering OVPD operation was established. The maximum surface current density at insulation‐defective interfaces was extracted as the corrosion model input. Electrochemical tests and surface analysis were used to evaluate U75V steel corrosion response. Results show that OVPD activation reduces corrosion severity and localization. When OVPD changes from open to closed state, the corrosion current density decreases from 12.47 to 2.57 μA/cm ² . Under the closed state, edge corrosion intensifies, with a peak current density of 3.44 μA/cm ² , higher than 2.45 μA/cm ² in the central region, accompanied by denser pitting corrosion. With increasing train intervals, corrosion current density decreases from 4.78 to 2.51 μA/cm ² as OVPD evolves from inactive to Stage‐I and Stage‐II. These results reveal the quantitative link between OVPD operation and corrosion response.