Augmentation of Polymer-FeCO Microlayers on Carbon Steel for Enhanced Corrosion Protection in Hydrodynamic CO Corrosion Environments.

Carbon dioxide (CO) 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) 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 layer on carbon steel can sometimes trigger localized corrosion. Our previous research demonstrated that poly(allylamine hydrochloride) (PAH) can work synergistically with FeCO when the corrosion product partially covers X65 carbon steel surfaces in an aqueous CO corrosion environment. In this study, we utilize rotating cylinder electrode (RCE) tests along with electrochemical measurements to investigate the FeCO-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 and FeCO-PAH hybrid layers using interferometry and focused ion beam scanning electron microscopy.