Interactions between cathodically protected pipelines and grounding systems
Buried pipelines carrying hazardous products are mandated to be protected against corrosion, generally via layer(s) of coating materials integrated with active cathodic protection systems. Impressed-current systems, normally adopted for larger or longer structures, force the pipeline to behave as a cathode, therefore providing protection against corrosion of its exposed parts when the coating fails. Cathodically protected pipelines may, however, be buried in proximity of grounding electrodes, such as ground grids of substations; thus, they may need to be bonded to the grid to prevent, or lower, the risk of metal-to-metal touch voltages, as indicated in applicable technical standards. This bonding connection, required for the safety of the electrical operators, may, however, compromise the effectiveness of the cathodic protection, as well safety. In this paper, the authors explore the issues introduced by the coexistence of grounding systems and cathodic protection systems, and propose possible solutions to insure safety and, at the same time, protect assets and the environment from corrosion.