The focus of metal powder coatings is to control the uniformity of color. Metal effect pigments are easily separated from powder particles during spraying. Even if the powder is bonded, it is difficult to achieve 100% adhesion of the metal effect pigments to the powder particles. Therefore, it is necessary to control the process to ensure the stability of the spray and reduce the separation.
Spray gun and its parameter selection
The powder will be better when the voltage is increased. At the same time, it will increase the separation between the metallic effect pigment and the powder particles, and increase the risk of electrostatic breakdown; reducing the voltage can reduce the separation between the metallic effect pigment and the powder, and reduce the gap between the new powder and the recycled powder. but also bring the disadvantage of low powder rate and more powder. For comprehensive consideration, it is recommended to reduce some voltages appropriately, such as 45-70kV. The specific values should be considered according to the shape of the workpiece to be sprayed, the position of the spray gun, the speed of the suspension chain, and the speed of the powder.
The atomizing pressure should be increased appropriately to increase the powdering speed. The difference between the effect of the gas flow on the metal effect pigment and the powder on the powder particles is small, which can reduce the influence of the electric field on the powder deposition.
The nozzle of the spray gun should use a flat mouth as much as possible to ensure the powder speed, help the powder, reduce the separation between the powder particles, and reduce the powder accumulation in the gun head. The nozzle is preferably equipped with a blowing device to blow off the accumulation of metallic effect pigments on the tip of the gun to prevent problems such as powdering and acne.
Metal powder coatings require a higher uniformity in spray thickness than conventional powder coatings. The thickness of the thin powder is generally weak, and the content of the metallic effect pigment tends to be different, which not only affects the covering and the orange peel, but also may cause significant chromatic aberration. The uniformity of the spray can be increased by increasing the number of spray guns.