When the car is sprayed, the paint is applied on the vertical surface, and the phenomenon of the paint flowing downward is called sagging. Sagging is one of the most common construction defects in automobile painting. Most of the sagging occurs in the raised parts of the sheet metal, corners and reinforcements.
1. The thinner is used incorrectly or the quality of the thinner is too poor (generally, the thinner with slow drying speed is used or the excessive thinner is used), which causes the paint viscosity to be too low.
2. The paint film of HVLP car painting is too thick, the pressure of compressed air is too low, and the paint cannot be opened; the fan of the car spray gun is too narrow, and the moving speed of the spray gun is too slow; the distance between the spray gun and the substrate surface will increase the possibility of sagging.
3. The paint layer of the one-time spraying of the automobile paint is too thick, which causes the paint layer to dry too slowly, or the paint spraying interval is too short, and there is not enough drying time for the previous paint layer.
1. Use the correct spraying method and adjust the automobile spray gun properly.
2. Use only the recommended type of thinner, and dilute the paint in the recommended ratio.
For larger sagging, you can use a scraper to treat the excess paint and smooth the surface. For smaller sagging, local fine grinding can be carried out, and then polishing, and the polishing wax should be gradually carried out from coarse to fine. In addition, it is necessary to maintain partial overall consistency.
It should be noted that if the varnish is accidentally worn out during polishing or the situation is serious, only the surface of the paint film can be polished and repainted. After the silver paint sags, delamination will occur, and the paint must be repainted.