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

Abstract

Carbon dioxide (CO 2 ) 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 (FeCO 3 ) can form on the internal walls of the pipeline, offering inhibition efficiency comparable to that of standard surfactant inhibitors. However, incomplete coverage of the FeCO 3 layer on carbon steel can sometimes trigger localized corrosion. Our previous research demonstrated that poly(allylamine hydrochloride) (PAH) can work synergistically with FeCO 3 when the corrosion product partially covers X65 carbon steel surfaces in an aqueous CO 2 corrosion environment. In this study, we utilize rotating cylinder electrode (RCE) tests along with electrochemical measurements to investigate the FeCO 3 −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 FeCO 3 and FeCO 3 −PAH hybrid layers using interferometry and focused ion beam scanning electron microscopy.