Exploratory Analysis into the Effect of Controlling Mechanisms within Mechanistic CO2 Corrosion Models (C2026-00087)

Michael Jones, Joshua Owen, Richard Woollam, Gregory de Boer, Richard Barker

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 for CO2 corrosion is investigated to explore how the rate-limiting mechanism influences the concentration of species at the corroding surface. Temperature, CO2 partial pressure, bulk pH 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 H+, Fe2+ and CO32- through the boundary layer. The FeCO3 saturation index is also calculated to assess influence of the controlling mechanism on the formation of protective surface films.