External Corrosion Risk Evaluation and Prevention Countermeasures for the Karamay Refinery–Fengcheng Oil Pipeline Based on Multi-Field Coupling

Oil transmission pipeline failures may cause severe ecological pollution, casualties, and economic losses, making pipeline corrosion safety management crucial. Existing corrosion evaluation models rely on generalized theories and rarely adopt field-measured data to analyze circumferential weld corrosion and degradation mechanisms under multi-physics coupling, resulting in inaccurate prediction of actual pipeline damage evolution. Taking the Karamay Refinery–Fengcheng oil pipeline as the research object, this study focuses on external corrosion induced by the soil environment, stray current, and overburden stress, since no detectable internal corrosion defects were found via inline inspection. The pipeline, originally designed for diesel transmission, actually transports heavy crude oil containing free water, sulfides, and inorganic salts, with an operating temperature range of 25–45 °C. This study establishes a practical coupled corrosion model via a second-order multi-field coupling framework based on field monitoring and global failure statistical data. Corrosion distribution, risk classification, and remaining service life are systematically analyzed, and targeted prevention countermeasures are proposed for pipeline segments with different risk levels. The results show that corrosion failure is the dominant pipeline failure type, with a maximum metal loss rate of 56.1% in electromagnetically interfered sections. Circumferential weld defects mainly accumulate on the right pipe crown due to laying gradients. The minimum remaining service life of high-risk segments under multi-field coupling is only 6.4 years. This study provides reliable technical support for the safe operation and maintenance of similar oil pipelines.