Abstract: To protect the AM60B magnesium alloy from corrosion, a sol–gel coating containing hydroxylated g-C₃N₄ nanoplates was applied. The chemical composition of the hydroxylated g-C₃N₄ nanoplates was investigated using X-ray photoelectron spectroscopy (XPS). The hydroxylation process did not affect the crystal size, specific surface area, pore volume, average pore diameter, and thermal stability of the g-C₃N₄ nanoplates. After incorporating pristine and hydroxylated g-C₃N₄ nanoplates, dense sol–gel coatings were obtained. Transmission electron microscopy (TEM) revealed the uniform distribution of the modified g-C₃N₄ in the coating. The average roughness of the coating was also reduced after adding the modified nanoplates due to the decreased aggregation tendency. Electrochemical impedance spectroscopy (EIS) examinations in simulated acid rain revealed a significant improvement in the anticorrosion properties of the sol–gel film after the addition of the modified g-C₃N₄ due to the chemical bonding of the coating to the nanoplates.