Development of a Predictive Model for Activation-Controlled Corrosion of Steel in Solutions Containing Carbon Dioxide

Corrosion of steel in carbon dioxide (CO₂)-containing solutions is considered a chemical reaction-controlled process. A corrosion rate equation was derived on the basis of fundamental reaction rate theory and compared to empirically determined relationships reported in the literature. The predictive equation was developed as a function of pH, partial pressure of CO₂ (⁠$PCO2$⁠), and temperature. The equation allows the inclusion of other variables, such as flow, impurities, inhibitors, and steel microstructure, through the reaction constant. The application limit for this equation extends to the point where corrosion becomes diffusion-controlled as a result of the formation of stable corrosion products on the steel surface.