Unlike wood, aluminium is slick and non-porous, making it a poor surface for paint adhesion. If you apply any kind of paint to a bare aluminium surface, you will see significant peeling and chipping over time. Many people are surprised to learn that there is no particular paint suited to coating aluminium. In reality, any paint will stick to aluminium as long as you use the proper base coat to abrade the aluminium to encourage adhesion.
No matter what kind of paint or primer you use on aluminium, it won't adhere if you haven't thoroughly cleaned the surface. Scrape away any dirt using a metal putty knife. Wash the surface using a water-based degreaser and a coarse plastic scrub brush. Rinse away all slick residue that may interfere with paint adhesion.
Before any paint will adhere to aluminium, it must be abraded. You can abrade wood, vinyl and plastic surfaces by scouring them with sandpaper. However, aluminium is too durable for friction techniques. Instead, you must apply an etching primer to the surface before you paint. Allow the primer to cure for at least four hours before you apply paint.
After you have abraded the aluminium with an etching primer, you can apply most any type of paint. Use a latex paint if the aluminium is located outside as this type of paint will move with the aluminium as it expands and contracts in varying weather. If the aluminium is located indoors, and you prefer a glossy appearance, you may use an oil-based enamel.
If you notice rust on your aluminium surface, you must remove and seal it before you apply any paint pr primer. Scrub away the rust using a wire brush and sandpaper. Then, coat the rust with a spray can of rust sealer.
Some paints claim to be specialised for coating aluminium. However, even these types of paints won't hold up over time unless they are applied over an etching primer. No type of paint will stick to bare aluminium unless it is properly abraded. Also, don't use a bonding primer in place of an etching primer or the finish will flake and peel.