Corrosion control of underground power cables

CORROSION OF underground structures is basically an electrochemical process which conforms to Faraday´s law of electrolysis. In anodic areas, current discharge from cables and pipes results in electrolytic corrosion at the annual rate of 75 pounds of lead or 20 pounds of iron loss per ampere discharged. Where the emf is external to the cables the corrosion cells may be caused by stray currents from d-c systems such as railways, or by electric connection of the lead cable sheath to more noble metals. Where the emf is internal to the cable sheath, corrosion cells usually result from exposure of the cable to an electrolytic environment in which variations exist in soil aeration, moisture, salt content, and texture. Soil bacteria probably are influential in causing differences in aeration in the soil and duct mud and thus generating a corrosion cell.