Effects of alternating current interference on the cathodic protection for API 5L X60 pipeline steel

In this work, the effect of alternating current (AC) interference on the cathodic protection (CP) of API 5L X60 pipeline steel was investigated using electro-chemical and mass-loss methods, as well as surface analysis techniques. The results demonstrate that, the corrosion potential of API 5L X60 steel shifts, and the polarization current density increases, with the AC interference. At a lower AC interference density, the existing standard CP potential (−850 mV (vs. a CSE)) can provide full protection for a buried API 5L X60 steel pipeline. However, at a higher AC interference density, the potential cannot ensure the safety of the pipeline. The results of a CP of −950 mV (vs. a CSE) demonstrate that a more negative CP potential can relieve the AC corrosion risk for buried API 5L X60 pipeline at higher AC interference densities. This finding benefits pipeline safety design and operation and weakens the AC-induced corrosion often observed in buried pipelines.