Clear Coating Polished Aluminum

Several suggestions for a water-clear finish on exterior metal hardware. September 3, 2011

Question
We're working on a jatoba entry door that has an unusual, custom made door handle. The handle is made from 1/2" plate aluminum cut on a CNC. The inside and outside pieces bolt to each other through the door, with spacers on each side. The deadbolt is separate. That's the easy part.

The hard part is finishing the handles. We are sanding in stages going up to 800 wet to achieve a polished look, which is no problem. We are having problems finding a finish to protect the polished look our customer is after. I know I can send these out for dipping but prefer to keep them in-house if possible. We are open to any finish supplier, but typically use SW products. Does anyone have any thoughts?

Forum Responses
(Finishing Forum)
From contributor C:
Matthews acrylic polyurethane is an outstanding exterior metal coating. Another one that I like is Akzo-Nobel Chromatic. Both of these stay water clear for a very long time. Sherwin Williams makes clear Polane which has an amber color in the can, but would probably work ok.

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From Paul Snyder, forum technical advisor:
My first choice would be to send it out for clear anodizing. There are probably other chemical dips/treatments that would also last a long time. Second choice would be a clear powder coat. If the budget was too tight for either of these options, I'd use a clear catalyzed polyurethane rated for exterior use. I use Matthews MAP a lot because I have a good local supplier that can match any color; it comes in gloss, satin, and matte; works well on a variety of substrates including plastics (start with "Tie bond"), metals, and wood; it's as durable as any other auto paint; sprays well; and polishes well. To clearcoat aluminum, start with "Spray Bond" and then topcoat with gloss MAP. You can probably get the same results from other brands of automotive clear coat, you'll just want to make sure they're compatible with raw aluminum.