Development of Calcium Carbonate-Based Coatings by the Carbonation of Gamma-C₂S (γ-C₂S)

A calcium carbonate (CaCO₃)-based coating with gamma-C₂S (γ-C₂S) as the main carbonatable binder is proposed to protect the metal substrate against corrosion in this paper. Here, the morphology and phase assemblage of the coatings are studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the corrosion resistance of the coating is evaluated by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). Results show that the carbonated coating has excellent properties in terms of ultraviolet (UV) aging resistance, salt fog resistance, and electrochemical corrosion resistance. The porosity of deposited coating on steel substrates decreases by 47.1% after carbonation due to the compacted calcium carbonate formation, which is recognized as a self-compacting process during carbonation. The coating also exhibits rapid strength development within the first 2 h of carbonation; both the CO₂ uptake efficiency and degree of carbonation (DOC) can reach more than 95% of the total CO₂ uptake efficiency and final DOC values. This study provides a novel insight to extend the category of inorganic coating with additional benefits of CO₂ solidification.