Anyone who has every tried to paint over anodized aluminum without priming first knows that chipping and peeling is virtually inevitable. Because anodized aluminum is slick and non-porous, it just doesn't hold paint very well. However, if you need to paint over anodized aluminum, there are a couple of preparation techniques you can employ that will allow you to achieve an attractive, long-lasting finish.
Clean the surface of the anodized aluminum using water, dish soap and a coarse brush. Rinse away all of the soap or you will have trouble with adhesion. Allow the surface to dry.
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Pour etching primer into a 1-gallon painter' s pot. Fill it to no more than two-thirds capacity.
Apply the etching primer to the anodized aluminum using the 2- to 4-inch paintbrush. Allow the primer to dry for two full hours.
Clean the brush at least three times using mineral spirits.
Apply oil-based paint to the anodized aluminum in the same manner as you did the primer. Allow the surface to dry for two hours. Apply additional coats as necessary.