Basically a cathodic protection unit consists of a source of direct current, the negative terminal of which is connected to the pipeline to be protected, and the positive terminal connected to the ground some distance from the pipeline. The ground connection is usually made by means of buried junk pipe or other expendable material, usually referred to as the ground bed. In operation, current flows in the conventional sense from the positive generator terminal to the ground bed, thence through the ground to the pipeline and from there to the negative terminal of the generator. By this means corrosion of the pipeline is. reduced, while corrosion of the ground bed is increased. Corrosion is transferred from the structure to be protected to a structure which can be replaced at relatively small cost.
All cathodic protection systems follow this general plan although in details they may differ widely. One line may...
