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by Ron Joseph

April, 2005

Clear Coating on Aluminum

Q. I am an artist. I have always worked in steel. I have a request to create a sculpture in aluminum. They are going to put it outside and want it to retain it's natural, shiny, silvery look. I know aluminum will oxidize and dull over time. My questions are:

How much time will it last before this occurs (ball park, we live in Colorado) and
What is the best clear coating system to use? Some research has pointed to powder coating and some to anodizing. Which would you recommend as the longer lasting and most affordable clear coat?

Thank you!

A. In my opinion clear anodizing will be much longer lasting than a clear powder coating on aluminum. I can't give you an approximate longevity as I don't have any information on this, and my is guess is that it will also depend on the aluminum alloy. On the other hand I would expect that the Aluminum Association might be able to assist you. Try http://www.aluminum.org/source/Orders/index.cfm?section=BookStore.

If you were to use a clear powder coating I would suggest that you consider a clear polyurethane, because this type of resin is known to have excellent performance under exterior exposure.

If you are willing to apply a liquid coating then consider a PVDF coating such as is described at http://www.vistawall.com/Skywall/press/finishes_for_arch_aluminum.htm.

I hope this gets you on the right track.

Best wishes,

Ron Joseph


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