It is not unusual to see paint peeling off gutters or downspouts.
Gutter, downspouts and duct work are all made of galvanized metal. The galvanizing process leaves behind oils that make it difficult for paint to adhere to properly.
Along with that, the zinc used in the galvanizing process will react negatively with oil-based paints and oil-based primers, causing the finish coat to peel away prematurely. With the right prep work and correct paint, painting galvanized metal is as simple as 1, 2, 3, 4, 5!
Step 1: If the galvanized metal has been previously painted, use a sandpaper or a wire brush to remove any loose paint and particles. Galvanized metal that has been weathered outside for less than two years may have a fine white film that will need to be sanded off completely.
Metals that have weathered for more than two years should have a hard white zinc patina that is actually the perfect surface for painting over. This hard white coating should not be removed.
Step 2: Clean the surface to be painted with mineral spirits or turpentine using several lint-free rags or soft nylon bristle brushes. Clean small areas at a time, being careful not to spread any residue from one spot to another.
Step 3: Once the surface is clean, thoroughly rinse with hot water and allow it to dry completely.
Step 4: Prime the area to be painted with a high-quality latex primer. Oil-based primers will interact with the zinc in galvanized finishes and cause premature peeling.
Water based primers such as Kilz 2 or Zinsser 1-2-3 Latex Primer will adhere properly to the galvanized metal finish and create a solid paintable surface.
Step 5: Finish the project with a top coat of high-quality acrylic latex paint. Acrylic latex paints will adhere well and provide exceptional durability and color. Use a good brush or smooth surface roller cover to ensure the best coverage.
If you choose to spray the finish on, make sure the paint is a latex acrylic and apply multiple coats to be certain the finish will last.