1. Lost light
The initial glossy coating surface gradually loses its luster during use, and the phenomenon that the coating is milky white like clouds is called gloss loss. When the loss of light is severe, micropores will appear on the coating film, and the mechanical properties will decrease. In electrostatic powder coating, the most important reason for the loss of gloss of the coating film is the interference between powder coatings of different resin types. For example, epoxy powder coatings, polyester powder coatings, and acrylic powder coatings will interfere with each other, so when the powder coating variety is replaced in actual production, the equipment is not cleaned, and the old and new powder coatings interfere with each other, which will cause the formed Coating film loses gloss.
2. Yellowing
The main reason for the yellowing of the coating film is that the baking temperature of the powder coating is too high and the time is too long. Sometimes in order to improve production efficiency, the method of increasing the baking temperature and shortening the baking time is adopted, but if the heat-resistant temperature of the powder coating is exceeded, yellowing and discoloration will occur, and the appearance and performance cannot meet the requirements, so the baking must be controlled. Roast temperature and time.
The cause analysis of coating film defects is listed in Table 6-1.
