1. Voltage

Electrophoretic coating adopts the constant voltage method, and the electrophoresis equipment is relatively simple and easy to control. The voltage has a great influence on the paint film; the higher the voltage, the thicker the electrophoretic paint film, and the coating ability can be improved correspondingly and the construction time can be shortened for the parts that are difficult to paint. However, if the voltage is too high, the surface of the paint film will be rough, and the phenomenon of "orange peel" will easily occur after drying. The voltage is too low, the electrolysis reaction is slow, the paint film is thin and uniform, and the swimming penetration is poor. The choice of voltage is determined by the type of paint and construction requirements. In general, the voltage is inversely proportional to the solid content of the paint and the paint temperature, and directly proportional to the distance between the two poles. The surface of steel is 40～70V, the surface of aluminum and aluminum alloy can be 60～100V, and the surface of galvanized parts is 70～85V.

2. Electrophoresis time

The thickness of the paint film increases with the extension of the electrophoresis equipment time, but when the paint film reaches a certain thickness, continue to extend the time, and the thickness cannot be increased, but it will aggravate the side reaction; on the contrary, the electrophoresis time is too short and the coating is too thin. The electrophoresis time should be based on the voltage used, and under the condition of ensuring the quality of the coating, the shorter the better. Generally, the electrophoresis time for workpieces is 1 to 3 minutes, and for large workpieces, it is 3 to 4 minutes. If the surface geometry of the coated object is complicated, the voltage and time can be increased appropriately.

3. Paint temperature

The coating temperature is high, the film formation rate is fast, but the appearance of the paint film is rough, which can also cause the coating to deteriorate; the temperature is low, the amount of electrodeposition is small, the film formation is slow, and the coating film is thin and dense. During the construction process, as part of the electrical energy is converted into heat energy during electrodeposition, the mechanical friction in the circulation system generates heat, which will cause the temperature of the paint to rise. Generally, the temperature of the paint solution is controlled at 15-30°C in some aspects.

4. The solid content and pigment-to-base ratio of the coating

The solid content of commercially available electrophoretic coatings is generally about 50%. During construction, distilled water is required to control the solid content of the coating at 10% to 15%. The solid content is too low, the hiding power of the paint film is not good, the pigment is easy to precipitate, and the stability of the paint is poor. If the solid content is too high, the viscosity will increase, which will cause the paint film to be rough and loose, and the adhesion will be poor. Generally, the ratio of pigment to base is about 1:2, and the ratio of pigment to base of high-gloss electrophoretic coatings can be controlled at 1:4. As the amount of paint in the paint will gradually decrease in actual operation, it is necessary to add paint with high pigment content at any time to adjust.

5. PH value of paint

The pH value of the electrophoretic coating directly affects the stability of the bath. If the pH value is too high, the newly deposited film will dissolve again, the paint film will become thinner, and the film will peel off after washing after electrophoresis. If the PH value is too low, the surface gloss of the workpiece is inconsistent, the stability of the paint solution is not good, the dissolved resin will be precipitated, the surface of the paint film is rough, and the adhesion is reduced. Generally, the PH value should be controlled between 7.5 and 8.5 during the construction process. In the construction project, due to continuous electrophoresis, cationic ammonium compounds accumulate in the paint, leading to an increase in the PH value. It can be used to supplement the stock solution with low PH value, replace the distilled water of the cathode cover, use ion exchange resin to remove ammonium ions, and use the anode cover to reduce the pH value. If the PH value is too low, add ethanol ammonium to adjust.

6. Paint resistance

The impurity ions brought by the coated object into the electrophoresis tank from the previous process cause a decrease in the resistance value of the paint, which leads to the appearance of roughness and unevenness of the paint film and pinholes. In the painting construction, the paint needs to be purified. In order to obtain high-quality coating film, cathode mask equipment can be used to remove ammonium, calcium, magnesium and other impurity positive ions

7. The distance between the workpiece and the cathode is 4 m

The distance is close and the deposition efficiency is high. However, if the distance is too close, the paint film will be too thick, resulting in sagging, orange peel and other ills. Generally, the distance is not less than 20cm. For large-scale and complex-shaped workpieces, when a very thick coating film has been deposited on the outside and the internal coating film is still thin, an auxiliary cathode should be added at a location far away from the cathode.