1 powder difference, falling powder
For example, in summer or rainy days, the air humidity is too high and the powder is damp. The metal powder itself is relatively poor in chargeability, the charge is led away, and the electrostatic adsorption is too poor, which not only reduces the powder rate, but if the suspension chain vibrates, it will cause the powder to form a plaque. Therefore, the air conditioner needs to be added to the air conditioner for dehumidification. In addition, the powder after unpacking needs to be resealed to prevent moisture if it is not used up.
2 pink pox
This kind of ills can be found before the curing after spraying. The powder layer after spraying has poor acne shape, and after curing, it shows prominent acne, and there are a lot of metallic effect pigments. In this case, some of the metallic effect pigments are generally not dispersed, such as poor powder atomization, moisture agglomeration of the powder, and accumulation of metallic effect pigments on the tip of the gun. Need to find a specific reason to exclude. When spraying metal powder, the spray gun preferably has a blowing device that can blow off the metal effect pigment accumulation of the gun head.
This phenomenon often occurs in areas where the coating is very thick. The powder rate on the metal powder is low, and the powder is too much. When spraying some workpieces, the falling powder will form powder in some parts of the workpiece, and the thickness can reach several times of the normal spraying. An excessively thick coating film causes a problem of blistering caused by poor degassing. It can be solved by strictly controlling the amount of powder, improving the suspension of the workpiece and improving the degassing performance of the powder.
4 dark spots
This ill appears as a tiny dark spot in appearance. Microscopically, the metal powder content is small, revealing the color of the base powder, resulting in a darker black color. It is often caused by poor dispersion of metallic effect pigments. It is possible to adjust the appropriate atomization parameters by adding an appropriate amount of a flow aid such as fumed alumina or silica to the powder.
5 aluminum powder corrosion
This situation often occurs after a period of time, and a dot-like, sheet-like discoloration occurs.
Aluminum powder as a metallic effect pigment has the advantages of bright white color and light weight, but the aluminum powder has poor corrosion resistance. Aluminum is an amphoteric metal that is chemically active and easily corroded by acid-base salts. Aluminum is particularly sensitive to corrosion by alkaline media. Aluminum powders for powder coatings are generally coated to reduce the corrosion of external chemicals. For powder coatings, it is necessary to select the appropriate corrosion-resistant aluminum powder according to your needs. Now the metal pre-treatment degreasing process generally uses alkali, and some of the front tank alkali liquid will be brought to the rear tank, and the metal workpiece remains partially alkalinized after a long time. The lye generally does not volatilize when heated, but instead concentrates, causing the aluminum powder to be corroded and discolored in the future. It is necessary to periodically check the pH value in the washing tank to prevent excessive alkalinity.