Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2003

Painting Aluminum

Q. I have a milled aluminum door bottom that will be attached to a wooden (poplar) screen door. (One of those neat-o Victorian style doors with all that scroll work.) I want to paint it white to match the door. The door will be west facing and have full sun most of the afternoon and evening. I live in Phoenix where 100+ degree summer days are routine, as well as 30-40 deg temperature swings in a 24 hour hour period during spring and fall. What kind of paint do I use and how should I prep the aluminum? I want to avoid the flaking, peeling, shrinking scenario.

A. Thanks for your question. Surface preparation of aluminum is the key to a successful paint job. Instead of purchasing your paint from a local hardware store, I suggest that you visit your local industrial paint store. Ideally, you should take the aluminum to a local custom coating shop (job shop) in Phoenix and ask them to prep the aluminum using a chemical immersion process. This should not be overly expensive, but it does mean finding a job shop and then taking the door bottom to them. After they have prepped the aluminum you can apply a polyurethane paint or an acrylic. The polyurethane that is used in industry has considerably higher performance than that which you can purchase from a hardware store. The job shop can easily apply the coating for you using a spray gun.

If you want to do the job entirely by yourself, then you will need to purchase an appropriate primer from the industrial paint store. I would suggest that you use a wash primer, but since this needs to be mixed strictly in accordance with the manufacturer's instructions and then applied with a spray gun, you might not be able to do so yourself.

After applying the wash primer you can apply an acrylic enamel or a polyurethane. The paint store folks will be able to give you the appropriate paints.

Please be aware, that if you have the door painted by a job shop you are considerably less likely to experience the peeling, flaking, problems that you wrote about. On the other hand, the do-it-yourself system will not give you the same degree of comfort. Paints do not stick well to aluminum, and unless you follow the correct procedures as can be accomplished by a job shop, you are likely to see the paint flake and peel within a few months.