All exposed metal surfaces (components) inside the electrophoretic tank and below the liquid level of the environmental protection electrophoretic paint shall be subject to insulation and anti-corrosion treatment. It is important to ensure the insulation between the tank body and the tank liquid. Otherwise, the inner wall of the tank or the exposed metal will be coated with paint during electrophoresis, and the paint film will fall and dissolve when electrophoresis is not performed, becoming particles with poor water solubility and polluting the tank liquid. In addition, the cathodic electrophoretic bath solution is acidic and has corrosive effect on the bath body, so anti-corrosion treatment is also required.
Therefore, the inner surface of the electrophoresis tank and the surface of all components (including overflow tank) in the tank shall be lined. The small electrophoresis tank shall be lined with PVC plate, and the large electrophoresis tank shall be coated with modified epoxy resin or unsaturated polyester fiberglass. The specific coating process points are as follows:
1. Before lining, the steel plate surface must be sandblasted to expose metallic color (silver gray), with a roughness of 40~70 μ m. To ensure the excellent adhesion of the coating, clean the treated surface and gap by blowing and suction, and reach the quality standard of sandblasting 3A.
2. Roll and brush a primer (modified epoxy or unsaturated polyester coating).
3. Cure at room temperature (about 20 ℃) for 8-10h.
4. Roll and brush two layers of primer, paste glass fiber cloth (or non-woven glass fiber fabric), quickly paste two layers, penetrate with paint, roll and smooth, use exhaust funnel to remove bubbles in the coating, and lay an additional layer of glass fiber cloth at the corner to increase the coating strength.
5. Cure at room temperature for 24h.
6. Grind off the glass fiber.
7. Roll and brush a layer of surface coating (modified epoxy or unsaturated polyester coating, white).
8. Cure at room temperature for 8-10h.
9. Carefully polish the flat coating surface (about 50% of the primer surface will be exposed after polishing) and clean the grinding dust.
10. Insulation inspection (high voltage resistance test) must withstand voltage of 15000V and prevent external carbon. The unqualified parts shall be repainted.
11. After the repair pressure is qualified, roll and brush the coating.
12. Curing.
Note: The modified epoxy or unsaturated polyester coating used is two-component or three-component (resin, curing agent, accelerator), and the ratio and viscosity shall be adjusted according to the recommendation of the supplier or site construction conditions.
