Galvanised sheet metal has a zinc coating that protects it from rust. This layer also inhibits paint adhesion. If you slap a coat of paint over unprimed galvanised sheet metal, paint failure will inevitably occur. Unfortunately, ordinary base primers won't adhere to galvanised metal. Select a special self-etching primer, specifically formulated for galvanised surfaces. Apply the etching primer and finish coat in a particular way, or flaws may appear in the finish coat.
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Things you need
- Water-based degreasing soap
- Steel wool or coarse plastic sponge
- Pressure washer
- Galvanised metal self-etching primer
- Nap roller cover
- Roller frame
- 4-inch polyester paintbrush
- Acrylic latex paint
Use steel wool or a coarse plastic sponge to scrub the galvanised sheet metal with a degreasing cleanser. Rinse the sheet metal, using a pressure washer or wet rags. Allow two hours dry time.
Apply self-etching primer to a 3-foot by 3-foot portion of the galvanised sheet metal, using a roller. Smooth the wet etching primer to promote a flawless finish. Brush the sheet metal in a vertical motion, applying gentle pressure. Continue until all of the sheet metal is primed. Allow the sheet metal to dry for three hours.
Wash the self-etching primer from the roller/brush, using water.
Paint the galvanised sheet metal just as you primed it. Wait three hours for the final finish to dry.
Tips and warnings
- Never use latex primer on galvanised sheet metal, or the finish will flake.
- Do not use a nylon brush to finish galvanised sheet metal, or flaws will appear in the finish coat.
- If you paint unprimed galvanised sheet metal, the finish will peel.