Study of A-C Sheath currents and their effect on lead-cable-sheath corrosion

The destruction of lead sheaths on underground cables by electrolysis usually is caused by the action of direct currents which originate from one or several well-defined sources. Little information is available concerning a-c electrolysis, and since the extent of its destructive action is less widespread than that produced by direct current it is considered generally to be relatively less important in the field of cable-sheath corrosion. This paper discusses two cases of electrolysis in which the lead sheaths on single-conductor power cables were corroded through, causing cable breakdowns; and describes field observations and laboratory tests which show that at first the corrosive action was accelerated greatly by rectified alternating currents which were induced in the sheaths by the load current. A method of protecting the sheaths against such electrolytic corrosion also is described.