Electrophoretic deposition has been in use since the 1960s, first for organic coatings and then to enamels. Compared with ordinary enamel, the enamel frit used in electrophoresis coating has no obvious difference. When grinding the enamel slip, only about 1.5% of clay is added. When electrophoresis coating enamel, the relative density of the enamel slip is 1.3~1.6, and the resistance is 300 ~400Ω. In order to prevent enamel precipitation, a stirring device is usually installed in the electrophoresis tank to keep the enamel slip in a fully suspended state. The process of electrophoretic coating is as follows:

(1) Activation of metal surface After degreasing and pickling of iron billet, it is activated at low temperature with diluted copper sulfate solution containing 3% hydrochloric acid.

(2) The galvanized iron billet is coated with a layer of zinc film in the electrolytic galvanizing tank. If there is no zinc film, the iron oxide formed by electrolysis penetrates into the white enamel deposit layer, and after firing, the porcelain surface produces macular spots. Although the galvanized layer will also oxidize, since the zinc oxide is white, it will not affect the color of the porcelain layer.

(3) The deposited iron blank of the enamel is immersed in the enamel slip with a density of about 1.58g/cm3 after being washed with water. The iron billet acts as the anode, and the cathode is inserted in a semipermeable membrane separated from the enamel enamel slip, through which only liquid and soluble ions can pass. Ion-enriched liquids are detrimental to operation due to increased conductivity in the cell. They can be removed by a semi-permeable membrane. Appropriate addition of some sodium aluminate to the enamel slip can improve the deposition properties of the enamel suspension. Ionized sodium aluminate releases positively charged sodium ions and is removed through the separator, hydroxide ions and alumina hydrates are negatively charged and deposited with the enamel frit, this type of alumina can increase the resistance of the deposited layer rate, so as to obtain a relatively uniform deposition layer. The pH, temperature and conductivity of the working tank must be strictly controlled so that the coating can be tightly adsorbed on the iron billet. After deposition, the powder blank enters the cleaning tank to rinse off the excess enamel. As the electrophoresis process continued, the enamel slip concentration decreased, the pH increased, the temperature increased, the iron ion concentration increased, and the powder quality deteriorated. After firing, the porcelain surface shows point and linear defects, and the color turns yellow. Therefore, it is necessary to frequently replenish new enamel slip, and add buffers (such as borax, etc.) to stabilize pH; at the same time, measures such as cooling and iron removal are adopted. There are many large auxiliary equipment in the electrophoretic coating production line, which requires a lot of investment. Therefore, only a few factories currently use electrophoretic coating. However, the enamel products produced by this process are particularly dense and smooth, without pinholes, and can withstand high voltages, so they are very suitable for making electronic accessories, such as enamel thick film circuit substrates.