Galvanized metal has special properties that can make it almost impossible for paint to stick to it. Although almost any paint may appear to adhere to galvanized metal, over time the zinc coating on the galvanized metal will react with the paint to create a slick, slimy film below the surface of the paint. This film will almost always cause the paint to chip or peel. In addition, most galvanized metal is coated with a slippery layer of oil to help prevent corrosion. This layer prevents paint from adhering, unless you know how to eliminate it before you get started. If you need to paint galvanized fence posts, use the proper preparation techniques for a long-lasting finish.
Trim grass and other vegetation away from the galvanized fence post, using a string trimmer.
Remove the layer of oil from the galvanized fence post using a water-based degreaser and a coarse brush. Rinse the galvanized fence post thoroughly with water.
Remove any rust or oxidation from the galvanized fence post using a wire brush. Skip this step if the galvanized fence post is new or in good condition.
Apply etching primer to the galvanized fence post using a 3- to 4-inch oil-based paintbrush. Allow the primer to dry for two hours.
Wash the etching primer from the 3-inch to 4-inch oil-based paintbrush using mineral spirits. Use your fingers to massage the mineral spirits into the bristles. Clean the brush at least three times.
Apply an epoxy-based galvanizing paint to the fence post. Allow the paint to dry for two hours. Apply another coat, if necessary.