Aluminum die casting parts are usually coated for appearance and anti-corrosion requirements. However, some factors will affect the quality of the coating, and even reduce the adhesion of the coating, affecting the performance of the castings.
1. The grease and release agent are not removed completely
For aluminum alloy products, special environmentally friendly degreasing agents should be selected. Common degreasers have little effect on mold release agents and can damage the surface of the material, and even cause discoloration of the product surface.
2. The thickness of the passivation film should be moderate
The trivalent chromium passivation film is uniform and dense, which can well enhance the adhesion between the coating and the substrate. However, care should be taken during the operation, and the film should not be too thin or too thick. If the film is too thin, the passivation effect will be poor; if it is too thick, the adhesion will decrease.
3. The quality of washing
Water washing after passivation is critical. Incomplete water washing can easily produce a secondary film on the surface of the passivation film, which also affects the adhesion of the coating.
4. The thickness of the coating
The thickness of the spray should be uniform, and attention should be paid to dust and wind during coating.
5. The baking temperature
The temperature in the oven should be constant and should not be hot or cold. If the temperature is too low, the coating will harden poorly, the adhesion will be poor, and the surface will be sticky; if the temperature is too high, the paint will be easy to age and crack.