Stray Current Corrosion Mitigation, Testing and Maintenance in dc Transit System

Stray current corrosion in direct current (dc) transit systems occurs because of the mechanism of current transfer between metals and a conductive electrolyte such as concrete, soil and water. Stray current reactions can be considered as a special case in that the anode (point of current discharge) may be at a considerable distance from the cathode (point of current pickup). The risk of stray current corrosion arising from the operation of dc-powered transit system is difficult to eliminate completely. However, suitable design of dc traction power systems and structures carrying the railways can significantly reduce the risk of corrosion both to the transit system structures and third-party structures.

Stray currents can cause safety risks, thus making the design of stray current mitigation, testing and maintenance an important element of the holistic design for a dc transit system. based on the results of the literature research, interviews with over two dozen dc rail transit systems, and testing of dc rail tracks, this paper presents and analyses various mitigation methods currently in use in the industry to control stray current corrosion. Recommendations for the testing (monitoring) and maintenance procedures to keep the stray current leakage and the related corrosion in control are then presented.