Summary for black chromic acid anodize Discussion
Black dyeing of chromic acid anodize is discussed as a process that may need lab development rather than a fixed recipe. Teddy McCracken asked how to black dye 2024 aluminum anodized with chromic acid, noting that his first attempt with Pylam Aluminum Black 801 and Alcor 570 sealer produced little or no color change and that final dimensions could not change. The excerpt does not show a detailed answer to his temperature question, but it does show a later reply from Robert H Probert, who advised starting in the lab and testing the dye on beakers with different pH and temperature settings for the specific circumstances. He suggested, once close, trying 0.1% by weight ammonium bifluoride in the dye solution and then briefly running the chromic anodic film back through deox before dyeing. The thread implies that black chromic acid anodize may require process tuning rather than a special pigment.
Q. I am seeking advice on how to black dye 2024 Aluminum that has been anodized using Chromic Acid. We have no experience with this operation and the first attempt yielded little or no color change. The products we use are:
Pylam Aluminum Black 801, 1.35 oz/gal, 60-70 °C Alcor 570 Sealer, 0.5- 1 oz/gal 60-80 °C
The final dimension of the pieces is critical and I would prefer to not make any changes(temperature, voltage, time…) in the anodizing process. How significant a role does the temperature of the dye play?
Teddy McCracken
– Blacksburg, Virginia, USA
2001
Ed. note: Accu-Labs, Inc. [a finishing.com supporting advertiser] now carries the Alcor line.
Q. What are the conditions that needed to obtain black chromic acid anodize aNorth Dakota does it require special pigment?
Limor Mictzeva
– Carmiel, Israel
January 6, 2013
A. Start in the lab to develop a process for your particular set of circumstances. Using the black dye you have, try different pH and different temperature in a beaker [beakers on
eBay
or
Amazon [affil link] . When you get close, then see what happens when you add 0.1 %/wt ammonium bifluoride to the dye solution. Finally, see what happens when you put the chromic anodic film, briefly, back through the deox before dyeing.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
January 8, 2013