Cracks of various lengths and depths.
1. Inappropriate paint system used on thermoplastic substrates (direct use of polyester body fillers/ fillers, wash primers/ synthetic resin products on TPA) which caused the TPA surface to soften
2. Refinished paintwork insufficiently cured (too little or no hardener used)
3. Inappropriate paint system used: Wash primer overcoated with polyester products Synthetic resin or nitro-cellulose paints overcoated too early
4. Cracks on plastic parts:
5. see entry on “Faults in painting plastics”
6. Exposure to strong UV radiation, extreme temperature fluctuations
7. Flash-off time too short in wet-on-wet process
8. Total film build too high
How to avoid
1. Apply a suitable paint system to the substrate.
2. Ensure correct hardener quantities.
3. Use correct paint system.
4. Plasticize materials.
5. There are no complaints about “cracking” with regard to present automotive refinish products.
6. Respect recommended flash-off times.
7. Check paint system and film thickness of old paintwork and sand down or strip down, if necessary.
Sand down to the “sound” layers. Refinish using the recommended undercoats and topcoats.