DURING the 1920’s the principal corrosion problems on underground structures were caused by stray current from grounded d-c trolley systems. The usual protective measure consisted of a “drainage wire” from the structure to the negative bus of the trolley generator. This lowered the potential of the structure below the potential of the earth in the vicinity of the drainage connection and consequently changed an anodic condition to a cathodic condition. This method was practical and effective where the corrosion exposure was reasonably close to the trolley generating station.
Where, due to some unusual condition, a corrosion exposure was created remote from the generating station the drainage method was not practical because the wire required would be too long and too large. G. G. Jones of the Long Lines Department of the American Telephone and Telegraph Company had several such exposures on his cables in Connecticut and Pennsylvania. He reasoned that...
