How to Make Paint Adhere to Galvanized Metal

Determine the age of the metal to decide how you will prepare it. Metal that is less than 48 hours old is considered new. Metal that has been in the elements for 48 hours to one year is considered partially weathered and is the most difficult to paint. Metal that has been in the elements for more than a year is considered fully weathered.

Remove any bumps or drips from the surface of the new or partially weathered metal using a hand grinder or hand sander. Grind or sand over the imperfection until the surface is flat. Bumps and drips on galvanized metal are caused by an excess of zinc during the manufacturing process and can’t be removed chemically.

Clean contaminants from the surface using a solvent cleaner for partially weathered or fully weathered metal. Spray or wipe solvent onto the surface of the metal and wipe away with a clean cloth. Change cloths often to avoid redepositing dirt on the metal surface.

Rinse the metal with fresh water repeatedly using a garden hose with a power nozzle attached. Allow the metal to dry completely for about 24 hours. This step applies to new, partially weathered and completely weathered metal.

Apply a wash primer to the metal to create a surface the paint can adhere to. Roll or brush the wash primer onto the metal and rinse if recommended by the manufacturer. Allow the metal to dry according to the manufacturer's directions.

Paint a few small areas of the metal and allow it to cure for seven days. Place a piece of masking tape on the paint and pull it off. If the paint comes off with the tape, re-apply the wash primer a second time to remove any unstripped coating.