Corrosion and Protection of Track Components by Stray Currents
What is stray current in rails, and what are its sources?
Stray current refers to abnormal current formed when DC traction current deviates from the normal return track and leaks into structures such as the track bed, bridges, tunnels, and pipelines. It mainly originates from poor insulation between the rail and the ground, excessive resistance at rail joints, insulation failure of fasteners, and excessively long rails leading to increased return voltage drop.
What is the corrosion mechanism of stray current on metal components?
After stray current flows into metal components, anodic electrolytic corrosion occurs in the outflow area: iron atoms lose electrons to become iron ions, leading to rapid corrosion, reduced cross-section, and decreased strength of the components. This corrosion rate is much higher than natural corrosion, and can cause severe corrosion of bolts, rails, and embedded parts within months.
Which rail components are most susceptible to stray current corrosion?
Metal components such as rail joint plates, bolts, rail spikes, fastener pads, sleeper embedded sleeves, bridge embedded parts, tunnel reinforcement, and grounding components are all prone to corrosion. Among these, bolts, joint plates, and embedded parts suffer the most severe corrosion due to their high current density.
What are the typical characteristics of stray current corrosion?
Corrosion is concentrated in the current outflow area, manifesting as pitting, pitting corrosion, rust nodules, and cross-sectional thinning; the corrosion rate is rapid and sudden; it is most severe at weak insulation points, joints, and damaged areas; compared with ordinary atmospheric corrosion, the corrosion is deeper and spreads faster.
What are the systemic protective measures against stray current corrosion?
Improve the rail transition resistance and fastener insulation performance; weld longer rails to reduce joint resistance; install stray current collection networks and drainage devices; use insulated gauge blocks, insulated pads, and insulated sleeves; regularly test insulation resistance and drainage status; strengthen the inspection and replacement of components in corroded sections.