Original Contribution to the Modelling of Corrosion Inhibitor Film Formation Dynamics on Carbon Steel in CO2-Saturated Produced Water from Nigerian Oilfields

Corrosion inhibitor film formation on carbon steel surfaces in CO2-saturated produced water from Nigerian oilfields is a dynamic, multi-step process governed by adsorption kinetics, competitive displacement, film morphology evolution, and electrochemical feedback that remains theoretically unresolved at the level of mechanistic detail required for inhibitor qualification and film persistence prediction. This study makes an original contribution to corrosion inhibitor film formation theory by developing a comprehensive mechanistic model that couples molecular dynamics simulation of imidazoline inhibitor adsorption at the steel surface, a kinetic Monte Carlo model for inhibitor island nucleation and growth, and an electrochemical film corrosion model for prediction of inhibitor performance as a function of injection history, flow velocity, and produced water composition. The theoretical framework is parameterised and validated using experimental data from a rotating cylinder electrode corrosion testing rig operated with synthetic produced waters representative of three major Nigerian oilfield chemical compositions from Imo, Rivers, and Akwa Ibom States. In-situ surface characterisation by atomic force microscopy and electrochemical impedance spectroscopy provided dynamic film formation data for model validation. The integrated model predicted steady-state inhibitor efficiency and film resistance within 11% of experimental measurements. An original film persistence coefficient is proposed, derived from the theoretical framework, which quantitatively predicts the time for inhibitor film degradation to safety threshold levels following injection interruption. The study contributes a theoretically rigorous and experimentally validated predictive tool for corrosion inhibitor management in Nigerian oilfield production systems. Keywords: corrosion inhibitor, film formation, CO2 corrosion, carbon steel, Nigerian oilfields