The Effect Of AC Interference On The Cathodic Protection Effect Of Buried Pipelines

With the rapid development of society, the energy industry and the transportation industry are also prosperous. At present, the extra high voltage power transmission has gradually entered into the construction of the power of our country. The space of development is limited and they would inevitably be laid out in parallel, crossed, or even sharing public corridors. In addition, the property of coating has been enforced, which leads to great improvement of insulation performance, so the grounding resistance of pipeline is reduced. In this case, AC interference becomes much more serious.At home and abroad, there are many controversies about the mechanism of AC corrosion, the ecaluation criteria of AC interference and the effect of the AC interference on the performance of cathodic protection system. So it’ s hard to estimate the effectiveness of the cathodic protection system in the field.This paper takes the AC interference condition of JN pipeline as the research object, and studies the effect of AC interference on the effectiveness of cathodic protection system by indoor corrosion simulation tests, including mass loss tests, electrochemical measurement and the corrosion morphology analysis. The aspects this paper mainly studies are as follows:Firstly, the cathodic protection status and AC interference condition of JN pipeline are tested. The frequency and the density of AC current in the experiments are determined by the field tests.Based on this, the indoor experimental project is designed.Then, the paper studies the effect of AC interference on the corrosion of pipelines by laboratory experiments, and the experiments mainly can be devided into three parts in general. First, in the absence of cathodic protection system, study the rule of AC corrosion by analyzing the variations of corrosion potential, polarization curves and corrosion rate under different AC current densities. For the second part, under the influence of AC interference the effectiveness of cathodic protection criteria no longer has any effect. This is found by mass loss tests and macrocosm appearance tests. The third part researches on variation of AC corrosion condition when the level of cathodic protection system is improved. By analyze the corrosion rate, level and efficiency of cathodic protection, this paper establishes the best cathodic protection potential and studies the influence of AC interference on the cathodic protection potential by analyzing the changes of DC potential and AC/DC unfiltered potential.Finally, this paper predicts the corrosion risk of JN pipeline and designs mitigation programe of AC interference based on the corrosion risk. At last, the peper evaluates the effectiveness of AC interference mitigation program. The evaluation results indicate that the mitigation program developed by the prediction of AC corrosion risk is effective.The study on the effect of AC interference on the effectiveness of cathodic protection system can predict the level of AC interference and the performance of cathodic protection system.This study also contributes to the design of mitigation measures. This paper is of great importance to ensure the safety of buried pipelines.