That doesn't mean you can't paint galvanized metal surfaces. Painting galvanized metal involves special preparation that must be properly performed to ensure a successful paint job.
Prepare the Surface
Prepare the metal surface by removing the protective coating on the galvanized metal. To do this, apply paint thinner over the entire surface. Sponge brushes make it easier to apply larger amounts of the paint thinner so you can work quickly. Wipe the surface of the galvanized metal with an old rag. Make sure to wipe thoroughly and let the metal dry completely. You won’t be able to use the rag again, so use something you don’t mind throwing out. It’s a good idea to wipe the surface again with a clean cloth after it has dried. Make sure to wipe off all the residue from the zinc coating and the paint thinner. If any residue remains, repeat the process with paint thinner.
Prime and Paint
Apply two coats of galvanized metal primer with a sprayer using short, even strokes that slightly overlap. Short strokes gives you more control and help conserve primer. Let the first coat dry before applying the second coat to prevent finish problems like bubbles or pitting. Let the last coat of primer dry completely. It shouldn’t feel gummy or tacky. Test a small spot on the surface by applying slight pressure with the tip of your finger. If your finger leaves a print in the primer, it is not dry. Once the galvanized metal surface is completely dry, apply a metal-grade paint. For an even coat of paint, use a paint sprayer rather than a brush. Brushes can leave brush strokes on the surface. Finish the project with a final coat of paint for the best coverage.