(1) The process flow of electrophoretic coating of general metal surface is: pre cleaning → online → degreasing → water washing → rust removal → water washing → neutralization → water washing → phosphating → water washing → passivation → electrophoretic coating → tank cleaning → ultrafiltration water washing → drying → offline.
(2) The substrate and pretreatment of the coating have a great impact on the electrophoretic coating. Generally, the castings are derusted by sand blasting or shot blasting, the floating dust on the surface of the workpiece is removed with cotton yarn, and the residual steel shot and other sundries on the surface are removed with 80 # ~ 120 # sandpaper. The steel surface shall be treated with oil and rust removal. When the surface requirements are too high, phosphating and passivation surface treatment shall be carried out. Ferrous metal workpieces must be phosphated before anodic electrophoresis, otherwise the corrosion resistance of the paint film is poor. When phosphating, zinc salt phosphating film is generally used, with a thickness of about 1 ~ 2 μ m. The phosphating film is required to be fine and uniform.
(3) In the filtration system, primary filtration is generally adopted, and the filter is a mesh bag structure with an aperture of 25 ~ 75 μ m。 The electrophoretic coating is delivered to the filter through a vertical pump for filtration.
(4) The circulating quantity of the circulating system of electrophoretic coating directly affects the stability of the bath solution and the quality of the paint film. Increase the circulation volume, and the sedimentation and bubbles of the tank liquid are reduced; However, the aging of tank liquid accelerates, the energy consumption increases, and the stability of tank liquid becomes worse. It is ideal to control the circulation times of tank liquid by 6 ~ 8 times /h.
(5) With the extension of production time, the impedance of anode diaphragm will increase and the effective working voltage will decrease. Therefore, the working voltage of the power supply should be gradually increased according to the voltage loss in production to compensate for the voltage drop of the anode diaphragm.
