In this surface issue, trapped solvents cause bubbles to appear on the surface. There are various causes for the occurrence of these bubbles.

Causes

1. The coating is applied too thick or heavy. 2. Use of inappropriate reducers (too fast drying). 3. Insufficient flash-off/drying time between spray coats. 4. High object temperature accelerates the drying process. 5. Excessive air drying time for two-component coatings before the object is placed in the oven. 6. Improper use of infrared lamps, where the lamps are too close to the surface, causing excessive surface temperature.

Prevention

To avoid bubbles, the correct reducer for the spraying temperature must be used, and the recommended coating thickness should not be exceeded. When temperatures are too high, slower reducers and hardeners must be used. In extreme heat, it may be necessary to reduce viscosity (i.e., add more reducer). Follow the correct flash-off times and drying temperatures, and ensure an adequate distance between the infrared lamp and the coated surface.

Repair

Surface damage (solvent bubbles) must be sanded down to where the bubbles occur, and the affected area must be recoated. Ensure all bubbles are fully removed during sanding to prevent pinholes after recoating.