An environmentally friendly chromium-free insulating coating suitable for oriented silicon steel was prepared by using aluminium dihydrogen phosphate, silica sol, water-based resin, sodium tetraborate and graphene aqueous dispersion as main raw materials. The morphology of the insulating coating was characterized by scanning electron microscopy. Corrosion resistance was investigated by neutral salt spray test and electrochemical test. Magnetic properties and surface insulating resistance were measured. The results showed that the surface of the insulating coating was flat; the addition of graphene could effectively improve the corrosion resistance and magnetic properties of the coating. The corrosion rate in the salt spray test was less than 10% after 120h, and the core loss was reduced by 9.57%. The addition of the graphene did not destroy the insulation properties of the coating. The surface insulation resistance per side of the coating was 269.51 Ω⋅mm2.
In this paper, graphene oxide (GO) is used as a matrix, and it is modified with a silane coupling agent (KH550) to prepare modified GO. The GO/waterborne polyurethane composite coatings with different contents are prepared by chemical grafting, and their structural characterization tests are carried out. The results show that the silane coupling agent can effectively modify GO, and the surface of the modified GO has more oxygen-containing functional groups. The added modified GO can effectively enhance the corrosion resistance of the coating, and the corrosion resistance of the composite coating was optimal when the mass fraction is 0.03%, and 5% corrosion occurs after 48 h, and the total corrosion time reaches 120h.
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