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.