Silicon carbide/enamel composite coatings for steel corrosion protection: Microstructure, thermal expansion behavior, and anti-corrosion performance

Vitreous enamel coating has been utilized to protect metallic substrates against corrosion and has proven to be effective. Herein, a new low-temperature sintering silicon carbide/enamel composite coating was produced and compared to pure enamel coating. The microstructure, thermal expansion behavior, and anti-corrosion performance of the prepared coatings were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), dilatometric test, and electrochemical measurements (open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR)). The results indicated that the composite coatings had gradually matched thermal expansion with the steel substrate due to the inclusion of silicon carbide and the raised porosity, which further resulted in the reduction of residual stress and the eradication of surface microcracks. The microstructural alterations increased the anti-corrosion effectiveness of composite coatings, according to the early electrochemical testing (at 24 h). Particularly, the polarization resistance (Rp) of a composite coating containing 7.5 wt% silicon carbide addition was found to be 20 times greater than that of the pure enamel coating. These results imply that the silicon carbide/enamel composite coating outperforms the pure enamel coating and can provide effective corrosion protection for steel. [Display omitted] •Silicon carbide/enamel composite coating was developed for steel corrosion protection.•Coating phases were segmented and quantified through grayscale threshold method.•Silicon carbide helped to reduce residual stress and eliminate microcracks in enamel coating.•Composite coating provided more effective corrosion protection than pure enamel coating.