A fully coupled model of hydrodynamic-chemical-electrochemical processes for CO₂ uniform corrosion in multi-physics environment

Carbon dioxide uniform corrosion occurs widely in the petroleum industry and threatens the safe production and transportation of petroleum resources. It is a complex issue involving a variety of physical, chemical and electrochemical processes in multiple temporal and spatial scales. A fully coupled model, taking into account all involved processes in a coupled fashion, such as fluid flow, multi-ion transport, multi-component chemical/electrochemical reactions, is established to comprehensively investigate the mechanism of CO₂ corrosion in multi-physics environment. The reliability of this model is validated by the good consistency between the predicted corrosion rates and the experimental results in the literature, and this model performs better in corrosion rate prediction than the previous models due to the explicit solution for the convective mass transfer. Based on this fully coupled model, the corrosion mechanism in the multi-physics coupled environments is revealed in terms of the time-dependent ion concentration field, mass transfer and electrode reaction kinetics. The interrelationship between the corrosion kinetics and the flow effect is explored. The results indicate that the time-dependent corrosion behavior is determined by the combined effect of the solution chemistry and electrical field. By accelerating the mass transport of corrosive species and the involved multi-component reactions, the fluid flow can significantly promote the corrosion process, while the promotion effect weakens gradually at higher flow velocities. Additionally, the flow effect at lower pH values is much more pronounced due to the transformation of the predominant controlling factors for electrode kinetics.