Ask the Expert Question-and-Answer Archive

by Ron Joseph

April, 2005

Clearcoating Aluminum for Exterior Application

Q. We are an architectural detail manufacturer (custom). We are bidding on some aluminum trellis for a commercial building. The customer wants us to sand/grind or scotchbrite for effect and then clear coat to prevent oxidation. My local paint supplier (Pittsburgh, pratt etc.) was not too comfortable recommending anything that he had. He did say I should look at automotive type paint to get a coating more resistant to peeling. He did have a two part but he guessed the coating life at 3 or 4 years. Any recommendations would be helpful. Thanks.

A. I would like to discuss the problem with you by phone because several decisions need to be made by you and/or your customer. Your paint supplier is correct. There are other high quality coatings that are designed to withstand exterior exposure for up to 20 years, but they must be applied by qualified and certified custom coating shops. A fluoropolymer, such as Kynar is what I have in mind, and you can find info on the web. Also, I would prefer to see you use a conversion coating pretreatment process rather than sanding, but the size and shape of the parts you intend to clearcoat might not allow for this.

If you would like to spend approximately 1/2 hour on the phone with me to discuss your options, please call at the phone number given below. I will need to charge a consulting fee of $100 payable by credit card.

Best wishes,

Ron Joseph