CATHODIC PROTECTION CURRENT REQUIREMENTS FOR ELECTRICAL GROUNDING MATERIALS

摘要

Although cathodically protected pipelines are often connected directly to electrical ground in stations and plants, there is little information on the amount of current required to polarize various grounding materials such as copper, tinned copper, stainless steel, silicon iron, and galvanized steel. This paper presents results of short and long-term cathodic polarization tests on commercially available grounding materials buried in a low resistivity clay and a high resistivity sand. The results indicate that in the non-aerated clay all the grounding materials, that would normally be cathodic to steel, required the same or less current density than steel. In the more aerated sandy soil, the current requirements for all the cathodic materials as well as steel increased by at least 2 orders of magnitude with copper requiting an increase of 3 orders of magnitude. Packaged zinc and magnesium anodes were also included in the testing program since they are occasionally used as grounding electrodes for cathodically protected pipelines.