Advancement in Predictive Modeling of Mild Steel Corrosion in CO₂- and H₂S-Containing Environments

Over the past decade, the knowledge related to predicting internal pipeline corrosion for sweet and particularly sour environments has dramatically improved. Advancement in understanding of the corrosion mechanisms related to H₂S corrosion environments enabled the development of an integrated electrochemical model for CO₂/H₂S uniform corrosion, including the effect of H₂S on the protective corrosion product formation on mild steel. The latest model of uniform CO₂/H₂S corrosion of carbon steel accounts for the key processes underlying of corrosion: chemical reactions in the bulk solution, electrochemical reactions at the steel surface, the mass transport between the bulk solution to the steel surface, and the corrosion product formation and growth (iron carbonate and iron sulfide). The model is able to predict the corrosion rate, as well as the surface water chemistry, as related to all of the key species involved. The model has been successfully calibrated against experimental data in conditions where corrosion product layers do not form and in environments where they do, and compared to other similar models.