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Black anodize for outdoor extrusions

September 30, 2011

We have been trying to get extrusions anodized so that they will withstand a color fade as they are used outdoors. We currently call out a mil-A-8625F-type 2, class 2 black, but when we do a UV test on the extrusion it is not holding the black and it goes back to looking like aluminum extrusion, AL6063-T5.

Apparently we are missing something. I do not know if we are not calling out the proper type of anodize for outdoor use or if we need to have it sealed. I have been working with several anodizers and we are obviously missing a step.

Any suggestions?

Lisa Barbuti
Purchasing - Morris, Connecticut, USA

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Sealing only goes so far with conventional black dyes despite the "light fastness" rating. You may need architectural anodize, a.k.a. 2-step, electrolytic coloring. Typically performed by extrusion houses for light poles, stadium seating and siding, it is specifically done for outdoor exposure. You may want to contact a firm like Keymark in Fonda, NY, who do this type of anodize.

Milt Stevenson, Jr.
Syracuse, New York
October 3, 2011