In order to keep the original paint on your steel garage door, wash it annually. Discoloration and chalkiness is the result of sun and dirt exposure. For regular cleaning, mix 1 cup of Simple Green and 2 gallons of water or mix 1 cup of household ammonia with five gallons of water. When washing go from the bottom to the top and use a soaking wet cloth, sponge, soft brush, or low pressure power washer. If mildew is not removed using this cleaning solution, try mixing bleach with five gallons of water. Make sure to rinse very well, because residues may damage the film. Before you start painting, prepare the surface. For dirt and mildew, mix 1 cup of Spic and Span with 5 gallons of warm water. For surface imperfections, lightly sand or buff, but make sure you don't expose the underlying metal. Once the metal is exposed there is a greater chance of rusting. For exposed metal and rust remove all loose rust or residue, then prime the door with a primer that will protect against rusting. For newly installed doors, there is a layer of wax that could cause the paint to not stick to the door. "To remove this wax, lightly scuff the surface with a GRAY (not green) 3M synthetic steel wool pad (equivalent to "000" steel wool) saturated with soapy water" (How to Repaint…). Once your door is prepped and ready for paint, make sure to paint it within 24 hours. Make sure the surface is completely dry and avoid painting in the morning or when temperatures are below 50 degrees.
