Localized corrosion of carbon steel in CO₂-H₂O environment is a long-standing challenge faced by the oil and gas industry, because of its unfeasible detection and high propagation rate. Numerical modelling can overcome the limitations of the spatial and temporal scales in the experimental studies, thus becoming a valuable complement. A multi-physics coupling model is established to investigate the evolution of localized corrosion of carbon steel in CO₂ aqueous environment. The complex interactions among the kinetics of electrode reactions, multicomponent reactions, mass transfer and the deposition of corrosion products are coupled into the model, achieving a comprehensive and physically realistic description of the actual corrosion process. The arbitrary Lagrangian-Eulerian method is implemented to track the moving metal/solution interface. Special emphasis is put on the coupling mechanism among the underlying processes at different time and length scales. This study characterizes quantitatively the time-dependent corrosion behavior, including the distributions of potential and species concentration within the corroding pit, corrosion current density and pit morphology. The inherent relationship between the corrosion behavior and the local corrosive environment within the pit is revealed. The results indicate that the competition between the chemical effect and electrical effect determines the trend and distribution of corrosion current density. The pit shape and cathode/anode area ratio have a great influence on the corrosion behavior due to the coupled role of local solution chemistry and electrical field.

中文翻译：

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CO2-H2O环境下碳钢时变局部腐蚀行为的多物理场耦合分析

碳钢在CO ₂ -H ₂ O环境中的局部腐蚀是石油和天然气工业面临的长期挑战，因为其检测不可行且传播速率高。数值建模可以克服实验研究中时空尺度的局限性，从而成为有价值的补充。建立了一个多物理场耦合模型，以研究碳钢在CO _2中的局部腐蚀的演变水性环境。电极反应动力学，多组分反应，传质和腐蚀产物沉积之间的复杂相互作用被耦合到模型中，从而获得了对实际腐蚀过程的全面而物理逼真的描述。实现了任意的拉格朗日-欧拉方法来跟踪移动的金属/溶液界面。特别强调在不同时间和长度范围内基础过程之间的耦合机制。这项研究定量表征了随时间变化的腐蚀行为，包括腐蚀坑内电位和物质浓度的分布，腐蚀电流密度和腐蚀坑形态。揭示了腐蚀行为与坑内局部腐蚀环境之间的内在联系。结果表明，化学效应和电效应之间的竞争决定了腐蚀电流密度的趋势和分布。由于局部溶液化学和电场的耦合作用，凹坑的形状和阴极/阳极的面积比对腐蚀行为有很大的影响。