Fish eye formation during powder coating: causes and solutions
Fish eyes are circular, open areas in the coating where the powder does not adhere to the substrate. These defects not only significantly impair the appearance, but also the protective effect of the powder coating. The good news is that fish eyes can be effectively avoided with the right preparation and system maintenance.
Typical causes of fish eyes
- Contamination on the workpiece: Oil, grease, silicone residues or release agents prevent the powder from adhering properly.
- Contaminants in the compressed air: Oil vapours or water droplets in the compressed air impair the powder quality and cause surface defects.
- Residues in the coating system: Contaminated powder lines, guns or nozzles can transfer foreign matter to the surface.
- Contaminated environment: Silicone-containing care products or cleaning agents in the vicinity of the coating system significantly increase the risk of fish eye formation.
Recommended solutions
- Thorough pre-treatment: Workpieces must be absolutely clean and free of grease. Use suitable cleaning and degreasing methods.
- Clean, dry compressed air: Use oil separators, water separators and maintenance units to ensure the quality of the compressed air.
- Regular system maintenance: Powder lines and guns should be flushed and cleaned regularly to prevent contamination.
- Silicone-free environment: Avoid the use of silicone-containing products in the areas of pre-treatment, coating and storage.
Conclusion
Fish eye formation can be almost completely prevented by using clean workpieces, high-quality compressed air, regular maintenance and a silicone-free environment. This is the only way to ensure perfect, visually and technically flawless coatings.
