Requirements for powder coating over hot dip galvanizing
The following specification is recommended:
- Use zinc phosphate pretreatment if highest adhesion is required. Surface must be perfectly clean. Zinc phosphate has no detergent action and will not remove oil or soil.
- Use iron phosphate if standard performance is required. Iron phosphate has a slight detergent action and will remove small amounts of surface contamination. Best used for pre-galvanized products.
- Pre-heat work prior to powder application.
- Use ‘degassing’ grade polyester powder coating only .
- Check for correct curing by solvent testing.
- Adjust pre-heat and line speed to ensure full cure.
- Hot dip galvanize and do not water or chromate quench .
- Remove all drainage spikes and surface defects .
- Powdercoat within 12 hours of galvanizing. Do not get surfaces wet. Do not leave outside
- Keep the surface clean. Do not transport uncovered loads. Diesel fumes will contaminate surface
- If surface contamination has occurred or is suspected, clean surface with proprietary solvent/detergent designed for pre-cleaning prior to powder coating .