RELATION OF LONG LINE CURRENTS TO SOIL CORROSION

Abstract

``Stray currents'' from street electric railways and the like give rise to rapid corrosion of buried pipe lines. A type of currents similar to ``stray currents,'' but which occur at long distances from any possible external source of electric current, has been found on pipe lines. These currents are known as ``long line currents'' and are supposed to originate between the soil and the pipe. They frequently follow the pipe for miles without any change in amperage. To determine possible influence of these currents upon corrosion, measurements of their value were made on an 8-inch oil line upon which much corrosion trouble had been experienced. The line was removed from the ground and the extent of corrosion determined by inspection. Electrical resistivities of numerous samples of soil were determined. From the data obtained, the following conclusions are drawn: 1. Discharge or accumulation of electric currents of the class which have been termed ``long line currents'' is, in general, without influence upon corrosion of buried pipe lines. 2. Electrical resistivity of soil correlates to a certain extent with corrosion of buried pipe; the relationship is not sufficiently consistent to be of practical value. 3. There is no consistent relationship between soil resistivity and the accumulation or discharge of ``long line currents.''