Color Fading of Anodized Aluminum

Letter 1065

Color Fading of Anodized Aluminum

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I do LASER engraving on anodized aluminum for botanical plates that are used outside. My supplier says that this material is for exterior use, however, after a few years the color on the plates seems to fade, especially on the ones facing south. I would appreciate your thoughts. Could this be UV rays causing the problem, and is this normal for anodized aluminum? I've sent a sample to my supplier for evalation.

Thank you,

Bill Kramer
LECOR Enterprises, Inc.

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SIR,

Every anodize dye has aq differnt lightfastness rating, meaning how well it hold up to outdoor light. some dyes are not suitable at all for outdoor use.

Also, a poor seal could cause color fading

David A. Kraft
Anacote Corporation

Long Island City, NY

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Bill,

You may want to look into electrolytic or the 2 step color anodizing. Light fastness is excellent.

Paul Davis

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Anodizers specializing in architectural applications will be most likely able to help you. They will need a 2 step (anodize then inorganic dye) process. The organic dyes just don't last as long in UV light. There is an anodizer in Minneapolis called Aacron - President is Don Johnson - one of the best at UV light resistance that we have found.

F.A. Sandy Donaldson
- Minneapolis

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Colors can only come from two sources; chromophores in organic chemicals that results from double bonds or triple bonds or a few other special bonds; in inorganics they come from metal ion complexes. UV light adds sufficient energy to break double or triple bonds so organic dyes are more susceptible to sunlight degradation. Try the inorganic metal dyes for outside use.

Dave Fairbourn
- Sandy, Utah

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Accelerated test of light fastness of colored anodized aluminium seems to be made by ISO 2135

The blu scale for evaluation is not easy to find anywhere and it is different from that one used for textile light fastness Could somebody tell me where can I find this special Blu scale to make this ISO 2135 test??

Many thanks G.Rizzotti

Gianmarco Rizzotti
- Busto Arsizio -Italy

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