Circular dents with raised edges appear on the coating surface, usually in the topcoat or intermediate layers.

Causes

1. Residue of oil, grease, wax, or silicone polish not thoroughly cleaned from the surface.

2. Contaminants in the air, such as spray mist from other types of coatings.

3. Oil or water mixed in the compressed air.

4. Silicones from aerosol cans (water repellents).

5. Foreign substances from nearby industrial plants.

Prevention

Thorough cleaning of the surface to be coated is essential to prevent cratering. If silicone-containing products (such as polishes or sealing compounds) are used, they must be applied in a separate area away from the spraying environment.

Repair

If craters have formed, sand off the affected coating layer, clean the surface thoroughly, and reapply the coating.