Painting galvanized metal requires some preparation to ensure proper adhesion and durability. Galvanized metal has a zinc coating to protect it from corrosion, but this coating can make it challenging for paint to adhere. Here's the best process:

1. Clean the Surface

Remove dirt and grease: Use a degreaser or soapy water to remove any oils, dirt, or grease from the surface. Rinse thoroughly and allow it to dry.
Eliminate white rust: If there is white rust (a chalky residue from the zinc), scrub it off with a wire brush or fine-grit sandpaper.

2. Scuff the Surface

Use fine sandpaper (120–150 grit) or a scuff pad to lightly roughen the surface. This helps the primer and paint adhere better.
Wipe down the surface with a clean, damp cloth to remove sanding dust.

3. Choose the Right Primer

Use a primer specifically designed for galvanized metal, such as a zinc-rich or self-etching primer. These primers adhere well to zinc-coated surfaces and create a good base for paint.
Apply the primer in thin, even coats according to the manufacturer’s instructions. Allow it to dry completely.

4. Select the Proper Paint

Opt for an acrylic latex paint or a paint specifically formulated for galvanized metal. Avoid alkyd- or oil-based paints unless they are explicitly labeled for galvanized surfaces, as these can react poorly with the zinc coating.

5. Paint Application

Apply the paint using a brush, roller, or spray, depending on the size and shape of the surface.
Use thin, even coats and let each coat dry completely before applying the next one. Typically, two coats are sufficient for full coverage.

6. Cure and Protect

Allow the paint to cure fully before subjecting the surface to heavy use or outdoor elements.
For additional protection, you can apply a clear sealant or topcoat if needed.

Tips:

New galvanized metal: If the metal is newly galvanized, it may have a shiny surface that makes adhesion difficult. Let it weather for a few weeks or use a vinegar solution (1:1 vinegar and water) to etch the surface before priming.
Test adhesion: Before painting a large area, test the primer and paint on a small, inconspicuous spot to ensure they adhere well.

Following these steps will ensure your painted galvanized metal is durable and looks great for years.