Effect of Copper Grounding on Cathodic Protection of Nearby Buried Steel Pipelines

To investigate the influence of copper grounding electrode on the cathodic protection potential and current distribution of buried pipelines, the constant potential polarization method was used to test the cathodic polarization behavior of copper grounding and pipe materials. The test results were combined with numerical simulation calculations to analyze the distribution of potential and current density in buried pipelines under the effects of three factors (polarization current density of copper grounding, pipe diameter, and grounding length) and their impact patterns. The equivalent circuit method was applied to theoretically analyze the influence pattern of pipelines affected by copper grounding. The results show that when the cathodic polarization current density for grounding increased, the grounding length increased, or when it was near other pipelines, the cathodic protection current absorbed by the grounding increased, leading to an increased loss of cathodic protection current for the buried pipelines. Copper grounding absorbed the cathodic protection current from adjacent buried steel pipelines, causing a positive shift in pipeline potential. The ground potential formed along the pipeline by the grounding current was one of the main reasons for the uneven distribution of pipeline potential. By forming an equivalent loop with the earth, grounding, pipeline, and anode, formulas derived from the equivalent circuit model were used to calculate the grounding current and its impact on pipeline potential distribution, which closely matched the simulation results. This could be used to predict the impact pattern of grounding on the cathodic protection of nearby buried steel pipelines.