Preparation and characterization of organic–inorganic hybrid coatings for improving the insulation properties of electrical steel

Phosphate has been used as a coating agent in various fields, such as electrical steel (ES), because of its excellent electrical insulation and corrosion resistance. Although the insulating properties of a phosphate coating can significantly improve the iron loss of the ES sheet, a new coating material to enhance the performance of the ES sheet further should be developed. In this study, we synthesized organic–inorganic hybrid coating agents with superior insulation compared to that of the conventional phosphate coating agent. Inorganic particles with excellent insulating properties (SiO₂, TiO₂, and Cr₂O₃) and silane coupling agents were used as starting materials. The good surface modification of inorganic particles by silane coupling agents with appropriate solvent content in the coating agent led to good dispersion stability of the coating agent. Homogeneous dispersion of the coating agent was attributed to the good surface roughness of the hybrid materials coated on the ES. Finally, when the hybrid coating agent with optimized composition was applied to the ES, the insulation property of the hybrid coating (< 100 mA) was superior compared to that of the conventional phosphate coating (~ 200 mA), and corrosion resistance was also excellent.