Description of problem:
Poor adhesion is usually noted in the workshop during the un-masking operation because of peeling problems.
Causes:
- Contamination of the painted surface with wax, silicone oil, grease, water, rust, soap, detergent, powder from the abrasive paper or discs, sanding residues, exhaust fumes, etc…. These impurities may come from the car, compressed air, workshop heater, roads and industrial facilities.
- Inappropriate ground coat either for the metal or the topcoat.
- Insufficient sanding.
- Primer had dried for several days before spraying the topcoat.
- Use of incorrect thinners.
- Masking of the first color in a multitone before it is fully dry.
- Color is left to dry too long before removing the masking paper.
- Flash off time too short.
- Condensation of substrate due to temperature changes.
Preventive measures:
- Make sure the surface is completely clean before painting.
- Use recommended ground coat.
- Sand adequately.
- Make sure that the temperature of the metal is not too high. Avoid spray dusts.
- Use recommended thinner and thinning ratios.
- Use recommended waiting times before application of the topcoat.
- Clean and prepare the bare metal.
- Use correct flash off time.
- Unmask at the right time.
Remedy:
Sand damaged area and repaint.
Note:
Peeling problems may be between the metal surface and the primer, the primer and the solid paint or the base coat and the clear coat. Normally the weakest link will give way.
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