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Why black anodized aluminum would turn gold from sun exposure

We have some black anodized aluminum parts that have turned gold from about six month exposure outside. What would cause this?

Dennis Berke
Product designer - St Paul, MN, USA
March 13, 2008

March 13, 2008

Most likely the dyes were not very lightfast, Dennis. Dyes are rated by their lightfastness although, in truth, black is probably not ideal for sun exposure. Architectural anodizing is "bronze" or "champagne" because these colors can be imparted with stable colors based on metals rather than dyes. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

The two step process (non dye) that Ted mentions can produce some dark colors that are quite fade resistant. A true black is not one of them.

James Watts
- Navarre, Florida
March 14, 2008

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