Numerical Study on Spatiotemporal Evolution and Quantitative Influence of Pitting Corrosion in Supercritical CO2 Pipelines under Mechanoelectrochemical Bidirectional Coupling

Summary

Supercritical CO2 is prone to induce pitting corrosion during pipeline transportation, leading to pipeline perforation failure. At present, most studies only consider the corrosion of pipelines under a single effect and ignore the influence of bidirectional mechanoelectrochemical coupling. However, under actual operating conditions, bidirectional mechanoelectrochemical coupling may complicate the pitting corrosion behavior. Focusing on X80 steel pipelines, this study incorporates the corrosion expansion theory and the regulatory mechanisms of stress on anodic equilibrium potential and cathodic exchange current density into the constitutive equation to establish a bidirectional mechanoelectrochemical coupling pitting evolution model. The spatiotemporal evolution of stress corrosion, electrochemical corrosion, and product film corrosion of pitting under bidirectional mechanoelectrochemical coupling was analyzed, and the expansion rules of pitting in horizontal and vertical directions were further explored. Additionally, the influence of bidirectional mechanoelectrochemical coupling on pitting was quantified. The results show that temporally, the stress, current density, and product film thickness in the defect area increase gradually with time. Spatially, the closer to the pitting center in the defect area, the greater the stress, the smaller the current density, and the thicker the product film. Pitting corrodes outward and downward in the horizontal and vertical directions over time, with the displacement increasing gradually and the rate of change first increasing and then decreasing. The corrosion parameters under bidirectional mechanoelectrochemical coupling conditions are 9.42–11.61% higher than those under simplified conditions, and the corrosion-induced stress promotes pitting corrosion. The research results provide theoretical support for pipeline corrosion prevention and control as well as safety optimization.