Corrosion Behavior and Comparative Assessment of Mitigation Alternatives for Buried Natural Gas Pipelines Under Urban Stray Current Influence—A Case Study of HVDC Grounding Electrode Interference

With the large-scale deployment of high-voltage direct current (HVDC) transmission projects, monopolar ground return operation has increasingly intensified stray current interference risks to adjacent buried metallic pipelines. This study investigates a high-pressure natural gas pipeline project in Guangdong Province by integrating field monitoring, soil resistivity measurements, polarization characterization, and numerical simulations to elucidate the potential distribution characteristics and corrosion evolution mechanisms under stray current influence. The results indicate that under an extreme operating condition of 1980 A, the pipe-to-soil potential shift ranges from −71 V to 69.9 V, significantly exceeding the safety threshold, while the maximum corrosion rate reaches 0.34 mm/y. Based on this, a combined protection system consisting of zinc ribbon drainage, deep-well drainage, and forced current drainage is further proposed. The selected mitigation scheme reduces the maximum corrosion rate to 0.0017 mm/y, demonstrating excellent mitigation performance. The results can provide theoretical and engineering references for the design, protection, and operation of long-distance pipelines in HVDC interference environments.