Mitigating reinforcement corrosion of basic magnesium sulfate cement concrete in marine environments: Comparative efficacy of corrosion-resistant rebars and inhibitors

Basic magnesium sulfate cement concrete (BMSCC) is a promising cementitious material for marine engineering, yet its low alkalinity poses a significant threat to the passivation of steel reinforcement. This study systematically investigates the regulatory mechanisms of various steel types and inhibitors within the BMSCC system. Utilizing linear polarization resistance and electrochemical impedance spectroscopy, the study evaluates the performance of conventional carbon steel, epoxy-coated, novel organic-coated, and 316 stainless steels, alongside traditional and pore-blocking compound admixtures. Critically, a specialized equivalent circuit model was developed to quantify the electrochemical parameters unique to the BMSCC-steel interface. Results reveal that while BMSCC is highly susceptible to chloride-induced corrosion, 316 stainless steel and epoxy coatings provide superior protection by compensating for the lack of a stable passive film. Furthermore, the study discovers that traditional calcium nitrite and amino alcohol inhibitors—highly effective in Portland cement—offer limited protection in BMSCC. In contrast, pore-blocking compound admixtures significantly enhance durability by densifying the BMSCC matrix. These findings provide a theoretical framework for selecting corrosion protection strategies tailored specifically to the unique chemistry of magnesium-based cementitious systems in marine environments.