Microstructure and Corrosion Resistance of Quartz Sand-Modified Enamel-Coated Steel Plates

Coating, as a corrosion protection measure, not only reduces the costs of repairs due to corrosion damage but also saves lives from injuries brought by corroded facilities or equipment. The corrosion behavior of quartz sand-modified enamel (QSME)-coated carbon steel plates was evaluated in a 3.5 wt.% NaCl solution for a period of 30 days using open circuit potential, electrochemical impedance spectroscopy (EIS), and linear polarization resistance. The enamel coating was made by firing enamel slurry to the steel plate at a temperature of around 840 °C. The effect of the size and content of quartz sand on the corrosion resistance is studied, considering four different contents (5 wt.%, 10 wt.%, 20 wt.%, and 30 wt.%) and two different particle sizes (0.38–0.83 mm and 0.83–1.70 mm). The microstructure and phase composition of QSME were characterized with a scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques. SEM images show that the thickness of QSME coating ranges from 430 to 1424 µm depending on the size of quartz sand, and the quartz sand is completely embedded in the enamel matrix. The QSME coating increases the corrosion resistance of uncoated steel plates by approximately 1000 times. The corrosion performance of QSME-coated plates decreases with an increase in quartz sand content, while the effect of the quartz sand size on the corrosion behavior is not significant. The QSME coating can be used to prolong the service lives of civil infrastructures subjected to chloride attack.