Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing 1989-2024
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Anodizing aluminum: dye is splotchy
Q. Hello, I'm a jeweler interested in using aluminum in my work. I tried anodizing an aluminum basket, about 0.5' square and 0.2mm thick and had a difficult time getting good results. After a lot of experimenting I was able to dye the basket fairly successfully, but wasn't really able to get an even consistent color. I'd appreciate any advice or insight that might help. Thanks!
James Peyton- Seattle, Washington
October 21, 2024
Aluminum How-To"Chromating - Anodizing - Hardcoating"
by Robert Probert
Also available in Spanish
You'll love this book. Finishing.com has sold almost a thousand copies without a single return request :-)
A. Hi James,
Unfortunately it is hard to narrow down what is wrong, all the way from cleaning to sealing.
• Are you sure there was no previous anodizing layer, or if there was, that you removed it?
• Are you sure the basket was spotlessly clean? If any doubt, scrub the basket with a tampico scrub brush, and a solution of powdered pumice and a dash of dish detergent before your normal cleaning.
• Did you do any etching or desmutting? If so, did the aluminum still look the color of raw aluminum before you proceeded.
• Was the anodizing done at reasonable current density (say 12 ASF), and did it look fine before dying?
• Are you using a high quality dye made for anodizing rather than a fabric dye? Did it already look inconsistent at this stage?
• What method and timing did you use for sealing? Nickel acetate would probably be ideal.
Send a pic of it to mooney@finishing.com for posting here.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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