Exploratory Analysis into the Effect of Controlling Mechanisms with Mechanistic CO₂ Corrosion Models

Mechanistic models of CO₂ corrosion are commonly used to predict how a system will respond to a given environment. These models not only predict the corrosion response, but also the speciation through the near-wall boundary layer, which provides useful information regarding the interfacial pH, as well as the propensity to form protective FeCO₃ layers. It has previously been shown that these models can also be used to predict the rate-limiting mechanism via the use of simulated polarization curves. By combining the simulated polarization curves with calculated values of surface concentrations, the interaction between the two can be explored. In this work, a comprehensive mechanistic model of CO₂ corrosion is investigated to explore how the rate-limiting mechanism influences the concentration of species at the corroding surface. CO₂ partial pressure and fluid velocity are varied within the model to adjust the controlling mechanism, which is then verified via simulated polarization curves. Speciation plots are extracted to show the corresponding impact on the concentrations of key species through the boundary layer. Contour maps of FeCO₃ saturation ratio and surface pH are also produced to assess the influence of the controlling mechanism on the formation of protective surface films.