How to improve the adhesion of topcoat to galvanized components?
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The components have been manufactured and are galvanized; the customer now wants a topcoat applied. I’m concerned that applying paint over the galvanized layer may result in poor adhesion of the paint to the surface. Do you have any good solutions?
1. After galvanizing, do not perform passivation; instead, use phosphating treatment. 2. After galvanizing, apply a phosphating primer with a thickness of 10 um; this will significantly improve the adhesion of the topcoat.
It is suggested to roughen the galvanized layer.
Recommendations: 1. Phosphating treatment; 2. Acrylic passivation; 3. Phosphating primer; 4. Sandblasting. Many types of paint can be used on galvanized parts, and sometimes the choice depends on the surface treatment. However, some coatings cannot be used on galvanized parts, especially oil-based alkyd paints. The most commonly used coatings for galvanized parts are epoxy coatings and water-based acrylic coatings. There are many types of epoxy coatings. They must be specifically designed for galvanized parts in order to be used. Epoxy will flake in sunlight, so it is best to apply an aliphatic polyurethane topcoat, which provides a good appearance and chemical resistance.
If a tall framework has already been installed, how should the treatment method be chosen?
“How is “sand sweeping” handled?
Sandblasting can be done in a workshop, but it’s probably not possible on large, installed frameworks. Furthermore, sanding of the hot-dip galvanized coating may not be thorough, thereby damaging the corrosion protection layer.