Study of Lower Temperature–Sintered Enamel Coating on Steel Bars: Effect of Coating Cycles

Abstract

Enamel coating is a novel type of coating for the corrosion protection of reinforcement in concrete. Recently, improved enamel coating was achieved using low-temperature sintering. This study aims to investigate the effect of coating cycles on the microstructure, adhesion, and corrosion resistance of a lower temperature sintered enamel coating. Enamel coated steel bars with single, double, and triple coatings (SC, DC, and TC, respectively) and uncoated (UC) steel bars were prepared. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectroscopy, and pull-off and salt spray tests were performed. The results showed that both the DC and TC had fewer defects and exhibited excellent corrosion resistance compared with that of the SC. However, the transition layer formed at the enamel/steel interface for the DC and TC steel bars weakened the coating adhesion. The related corrosion mechanism was illustrated based on two different corrosion modes: corrosion that occurred at holes (COH) and corrosion that occurred at microcracks (COM).