Augmentation of Polymer-FeCO3 Microlayers on Carbon Steel for Enhanced Corrosion Protection in Hydrodynamic CO2 Corrosion Environments

Carbon dioxide (CO₂) internal corrosion of carbon steel pipelines is a significant challenge and is typically managed by adding corrosion inhibitors. In certain operational conditions, a natural protective layer of iron carbonate (FeCO₃) can form on the internal walls of the pipeline, offering inhibition efficiency comparable to that of standard surfactant inhibitors. However, incomplete coverage of the FeCO₃ layer on carbon steel can sometimes trigger localized corrosion. Our previous research demonstrated that poly(allylamine hydrochloride) (PAH) can work synergistically with FeCO₃ when the corrosion product partially covers X65 carbon steel surfaces in an aqueous CO₂ corrosion environment. In this study, we utilize rotating cylinder electrode (RCE) tests along with electrochemical measurements to investigate the FeCO₃-PAH hybrid structure in a dynamic environment. We characterize the general and localized corrosion behavior as well as the surface properties of both naturally formed FeCO₃ and FeCO₃-PAH hybrid layers using interferometry and focused ion beam scanning electron microscopy.