Augmentation of Polymer-Corrosion Product Layers on Carbon Steel for Enhanced Corrosion Protection in Hydrodynamic CO₂ Corrosion Environments

Carbon dioxide (CO₂) internal corrosion of carbon steel pipelines remains a major issue that is typically mitigated via the addition of corrosion inhibitors. In specific operational environments, a protective natural corrosion product layer known as iron carbonate (FeCO3) can evolve on internal pipeline walls, providing comparable inhibition efficiency to that achieved from typical oilfield surfactant inhibitors. However, in some instances, partial coverage can initiate localized corrosion. In our previous work, we demonstrated the ability of Poly (allylamine hydrochloride) (PAH) to act synergistically with FeCO₃ when the corrosion product exhibits partial coverage of X65 carbon steel surfaces in an aqueous CO₂ corrosion environment. In this work, we employ Rotating Cylinder Electrode (RCE) tests coupled with electrochemical measurements to study the FeCO₃-PAH hybrid structure in a hydrodynamic environment. The general and localized corrosion behavior, as well as surface properties of a naturally formed FeCO₃ and the FeCO₃-PAH hybrid layers are characterized, employing interferometry and scanning electron microscopy (SEM) coupled focused ionic beam (FIB).