Long-Term Corrosion Mechanisms and Resistance of Steel Bars Coated with Quartz Sand-Modified Enamel Embedded in Mortar

In this study, the long-term corrosion performance of steel bars coated with quartz sand-modified enamel (QSME) in mortar cylinders was studied by immersing them in a sodium chloride solution for 540 days. The effects of steel bar type, quartz sand content, and quartz sand particle size on the corrosion resistance were investigated. For comparison, enamel-coated and uncoated specimens were also tested. The microstructure before and after corrosion tests was characterized using scanning electron microscopy. The corrosion behavior was assessed using linear polarization resistance, impedance spectroscopy, and potentiodynamic polarization. Results show that QSME coating has a thickness ranging from 464 μm to 735 μm depending on the quartz sand size and the steel bar deformation. QSME can effectively protect smooth and deformed steel bars, with the QSME containing 10.0 wt.% quartz sand exhibiting the highest corrosion resistance, while 30.0 wt.% quartz sand indicates the lowest corrosion resistance. The presence of microcracks within the quartz sand particles is the primary factor that diminishes the corrosion performance of QSME coatings.