Abstract: Taking phosphate and ammonium metavanadate as the primary raw materials, a low-chromium phosphate coating solution was prepared for grain-oriented silicon steel with a magnesium silicate underlayer. Upon heat treatment at over 800℃, the prepared coating solution develops a compact and dense insulating film. Phase composition analysis reveals that the coating consists of amorphous oxides or composite oxides of aluminum, silicon, magnesium and vanadium, along with a small amount of phosphorus-containing oxysalts. The grain-oriented silicon steel specimen with low chromium insulating coating exhibit excellent corrosion resistance in 3.5%(mass fraction) NaCl solution. Polarization curve analysis shows that the self-corrosion potential of the low chromium coated sample is -0.563V, and its polarization resistance R_p is up to 24425.5Ω. Electrochemical impedance spectroscopy results demonstrate that the surface micropore resistance R_po is 592.4Ω·cm² and the charge transfer resistance is 20840.0Ω·cm², respectively, which endows the material with favorable corrosion resistance. The average iron loss of grain-oriented silicon steel sheet is reduced by approximately 12.28% under the protection of the low-chromium insulating coating, which is comparable to that of the reference chromium coating.

Key words: grain-oriented silicon steel, phosphate coating, low-chromium coating, corrosion resistance, iron loss