Electrochemical Factors In Underground Corrosion of Lead Cable Sheath^⋆

Stray current is the principle cause of corrosion failures on underground telephone cables in most cities where trolleys are operated. To mitigate this condition, the cable sheaths are “drained” to the negative return system of the traction system. By this means not only is the stray current anodic area largely eliminated, but the cables automatically become negative to earth, and therefore are cathodically protected. The cathodic protection afforded in this manner prevents other types of corrosion from occurring. With the gradual abandonment of trolley systems, and with the extension of underground cables into non-trolley areas, the percentage of underground telephone plant receiving this protection is decreasing. As a result, the problems of lead corrosion due to such causes as galvanic and local cell action of various types, and chemical action by substances in the soil are becoming more prevalent. It is the purpose of this article to review some of...