The following information has been reprinted from the American Galvanizers Association publication "Duplex Systems: Painting Over Hot-Dip Galvanized Steel."
Occasionally, galvanized steel is damaged during handling, fabrication, installation or welding. These damaged areas should be repaired according to ASTM-A780-93 Repair of Damaged and Uncoated Areas of Hot Dip Galvanized Coatings. Brite Products, Brite Zinc met and exceeded this standard. Proper repair ensures the galvanized coating provides the best corrosion resistance possible. When using a duplex system (primer and topcoat), any damaged area on the galvanized surface must be repaired prior to painting. The following steps help ensure the galvanized steel is adequately repaired and able to perform compatibly with a paint system.
- Depending on the age of the galvanized product, properly prepare and clean the surface of the material to be painted before applying the touch-up product.
- Touch-up damaged areas with a product conforming to ASTM A 780. These include paint products that are commonly known as zinc-rich paints, or cold galvanizing compounds. Zinc-rich paints can be sprayed or brushed on the damaged area.
- After touch-up, prime the surface to be painted. As a protective system, zinc-rich paints (like Brite Zinc) provide the best galvanic protection for long-term exposure.
- If required, finish with a topcoat. Follow the manufacturers guidelines for proper dry times and surface preparation between coats.