There are two types of coatings: enamel and varnish. Enamel contains fillers or pigments, while varnish does not. Coatings are used to coat the surfaces of impregnated electrical coils, insulators, and metal structural components to achieve various purposes, such as isolating them from air, preventing oxidation and aging, improving corrosion resistance, moisture resistance, and chemical resistance, improving thermal conductivity, and increasing the commercial value of the equipment.
The performance requirements for topcoat varnishes include fast drying, strong adhesion, hard film, high mechanical strength, moisture resistance, oil resistance, and corrosion resistance. Enamel films have a higher hardness than varnishes of the same base, and offer better thermal conductivity, heat resistance, and arc resistance, but other electrical properties are slightly inferior. It is mostly used for coating coils and metal surfaces. Varnishes are primarily used for coating insulating components and the inner surfaces of electrical equipment.
Commonly Used Topcoat Paints: Types, Models, Characteristics, and Applications
J-813 polyurethane air-drying paint: heat resistance grade E, fast drying, tough and glossy paint film, stable performance.
●1231 Alkyd Drying Topcoat: Heat resistance grade B, heat resistance grade E, with good elasticity and high dielectric properties, used for covering electrical appliance surfaces.
●9120 epoxy ester drying varnish: heat resistance grade B, glossy, strong, and weather-resistant film, used for covering the surfaces of motors and electrical appliances.
●162 Epoxy Ester Red Ceramic Paint: Heat resistance grade B, the paint film is hard, smooth, high strength, resistant to bacteria and has high dielectric properties, used for covering the surface of motor and electrical windings.
●163 Epoxy Ester Gray Enamel: Heat resistance grade B, performance is the same as type 162, but contains anti-mildew agent, used for covering the windings of motors and electrical appliances in tropical regions.
●164 Epoxy Ester Gray Enamel: Heat resistance grade B, low drying temperature, other properties are the same as type 163, used for covering the surface of motor and electrical windings in humid tropical regions.
●165 Polyester Gray Enamel: Heat resistance grade F, hard and smooth film, strong adhesion, resistant to mineral oil, and has good moisture-proof and mildew-proof properties. It is used for covering the surface of motor windings and electrical windings.
●166 Polyester Drying Gray Enamel: Heat resistance grade F, hard and smooth enamel film, resistant to mineral oil and with good moisture resistance, used for covering the surface of motor stator windings and electrical windings.
●182 Polyester Dry-Dry Crimson Enamel: Heat resistance grade F, good dielectric properties, oil resistance and elasticity, used for covering the surface of motor rotor windings and electrical windings.
●183 Polyester Drying Iron Red Enamel: Heat resistance grade F, with good dielectric properties, water resistance and elasticity, used for covering the surface of motor rotor windings and electrical windings.
●184 Polyester Drying Lake Blue Enamel: Heat resistance grade F, performance is the same as type 183, used for covering the surface of motor rotor windings.
●9129 Epoxy Solvent-Free Topcoat: Heat resistance grade F, the coating film has high hardness and good elasticity, used for coating the stator end surface of a 600MW steam turbine generator.
●185 Organosilicon Alkyd Enamel: Heat resistance grade H, with good electrical and mechanical properties and resistance to tracking, used for coating dry outdoor reactors.
●169 Polyester Modified Silicone Red Ceramic Paint: Heat resistance grade H, with good adhesion, moisture resistance and elasticity, used for moisture-proof coating of motor windings and electrical components.
●9131 Organosilicon Enamel: Heat resistance grade H, with good heat resistance, oil resistance, moisture resistance and electrical insulation properties. The enamel film does not become sticky after drying. It is used for covering the surface of H-class motor and electrical windings.
●167 Organosilicon Drying Red Enamel: Heat resistance grade H, with high elasticity, oil resistance and dielectric properties, used to decorate the surface of motor windings.
●197 High-purity polyester modified silicone paint: Heat resistance grade H, low curing temperature, high mechanical strength, strong adhesion, dense paint film, low air permeability, suitable as a surface protective coating for high-power semiconductor devices and thyristors.
Features and precautions of air-drying topcoat
Air-drying cover coats do not require baking, but their performance is inferior to oven-dried cover coats. They are mainly used for coating the surfaces of large electrical equipment or parts that are not suitable for baking. However, for parts that are suitable for baking, oven-dried cover coats should be used whenever possible.
When using coating paint, strict control must be exercised over its viscosity and uniformity, baking temperature, and environmental cleanliness; otherwise, the drying and surface quality of the paint film will be affected. Enamelled paints contain fillers or pigments, which can easily lead to sedimentation, clumping, uneven viscosity, and discoloration during storage. Therefore, the paint should be thoroughly stirred before mixing and use. If a skin forms on the paint surface, it should be carefully removed or filtered before use to prevent it from contaminating the paint and affecting the surface quality of the paint film.
Topcoat paint can be applied by spraying, brushing, or dipping, and usually requires multiple coats, typically two .
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