Introduction of Electrostatic Enamel Coating

One of the greatest achievements of the enameling process is dry electrostatic enameling. The main advantages of dry electrostatic enameling of enamel powder are: 1. The utilization rate of enamel can be as high as 97%~98%. 2. Improve the gloss of the porcelain surface and reduce the defects of the porcelain surface at the edge. 3. The two-pond and one-burning process can be used, and no special decarburized steel plate is required. 4. The dry powder of enamel is used directly without grinding into enamel slurry, and the drying process after spraying is omitted.

The dry electrostatic spray enamel system includes electrostatic spray gun, elevator, powder supply barrel, material supply and return system, filter screen, magnetic separation device, spray booth, and recovery system. 

The electrostatic spray gun adopts the principle of high voltage generation. The gun head forms a negatively charged electrostatic field under a voltage of 70~100kV. The workpiece to be sprayed is grounded. When the workpiece passes through the spray gun in the spray booth, the spray gun begins to spray powder, positively charged workpieces and negatively charged workpieces The powder is attracted to each other to form a powder coating. The oversprayed powder is pumped back to the filter system, passed through the filter screen and the powder supply barrel, and recirculated to the spray gun. 

Compared with ordinary organic powder, enamel powder has the following characteristics: 1. Strong abrasiveness. 2. High density, 2~3 times that of organic powder. 3. The enamel powder is wrapped with organosilane to control the static characteristics. 4. Sensitive to relative humidity. 

Compared with organic paint powder, ordinary enamel powder has two shortcomings:

Resistivity: organic paint 1016~18Ω•cm, enamel frit 106Ω•cm.

Density: 1.1 g/cm3 for organic paint, 2.5~2.7 g/cm3 for enamel frit. 

The charged organic particles are attracted by the iron billet and will not lose their charge after being adsorbed. Although the charged enamel particles can be deposited on the iron billet, they will quickly lose their charge and fall off due to their low resistivity and high density. The solution is to wrap the enamel with organosilane. Through this treatment, the resistivity of the enamel can be as high as 1014Ω•cm. 

The fine particles of enamel wrapped with organosilane are suspended in a fluidized bed and transported to an electrostatic spray gun for spraying. The voltage used is generally not higher than 100kV. The coating strength of electrostatic powder deposition is low, so the powder can not be touched when transporting the powder to the furnace chain. It is very convenient to use the hook to transfer from the spraying line to the firing line. 

Since there is no need for abrasive additives such as clay and electrolyte, the gloss and acid resistance of the porcelain layer after powder coating and firing have been improved. Because it is not possible to grind and add pigments, the products produced by dry powder electrostatic spray enamel are mainly white and black, and the color is relatively monotonous.