A mechanistic model CO2/H2S corrosion of mild steel in the presence of trace amount of H2S has been developed. The model predicts accurate solution chemistry at the metal surface and it is capable of predicting the rate of iron sulfide and iron carbonate film growth, the change in morphology and composition of the film with respect to space and time, as well as the resulting corrosion rate time evolution.
The model has been successfully calibrated against data from a large number of carefully controlled corrosion experiments under different environmental parameters in the presence of trace amount of H 2 S, in both film free and film forming conditions. Parametric testing of the model has been done in order to gain insight into the effect of various environmental parameters on mixed films formation and the resulting corrosion rate. The trends shown in the predictions agreed well with the general understanding of the CO2/H2S corrosion process in the presence of iron carbonate and iron sulfide films.