There are usually three kinds of enamelling and one-firing processes for enamel products: wet-wet, dry-dry and wet-dry processes.

The "wet-dry" two-enamelling and one-firing process is to apply the ground coat slurry containing an adhesive, then completely dry, and then spray the dry powder cover coat on the dry ground coat by electrostatic spraying.

The advantages of the "wet-dry" enamelling system are:

1. It is suitable for mass production of dish products with a limited number of colors (white and big cyan);

2. Since the powder is sprayed with low pressure, a smooth enamel surface can be obtained;

3. Compared with the dry-dry process system, the bubble structure of the ground coat is easy to control, and adding quartz through the ground coat grinding can make it possible to enamel on both sides;

4. Compared with the dry-dry enamel process system, the thickness of the ground coat layer can be changed without affecting the final surface coating, and the thickness of the ground coat can reach 80μm. In this process, the edge effect is very important for the electrostatic spraying of the ground coat;

5. Due to the electrostatic effect and Faraday cage effect, the ground coat layer after drying has no mixed penetration;

6. It has a greater scope of adaptation to the design of complex products;

7. There is no possibility of electrostatic interaction between the bottom and cover coat, and the number of spray guns can be reduced when spraying dry powder enamel. Since the ground coat layer has no mixing and interpenetration after drying;

8. Compared with the "dry-dry" enamelling process system, the "wet-dry" system seems to be more likely to be applied.

The disadvantages of the "wet-dry" enamelling system are:

1. The color selection of dry powder enamel will be limited;

2. In this process, powder spraying should be carried out in an air conditioning room with constant temperature and humidity;

3. If bilateral glazing is required, zero carbon steel can be used.

Whether it is wet-wet, dry-dry or wet-dry enamelling system, it is based on white primer, which has a relatively high proportion of adhesion-promoting oxides in the composition of white primer, which has good wetting to metal Therefore, the use of this system can not only improve the interface bonding strength, but also simplify the pretreatment of the steel plate. The steel plate does not need to be pickled, but only degreased.

Good results can be obtained with normal enamelled steel grades when using the "wet-wet" system with two enamelling and one firing. For the "dry-dry" enamelling system, decarburized steel sheets can be used, especially when enameld on both sides, the "dry-dry" enamelling process is very favorable for enamelling decarburized steel sheets. In the "wet-dry" system, only decarburized steel sheets have been used so far.