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Stripping solution and masking agent for anodizing

I was contacted by a fellow today who wishes to have some decorative anodizing done on one of his paintball markers. I have been anodizing successfully now for many months, however, to date I have worked solely with bare aluminum. In this case, I will have to strip the already black anodized layer from his marker before I go ahead and prepare it for a fresh look. I realize that one could utilize his/her etch bath as a means of stripping, however, I feel that this method is simply far too uncontrolled. I do not wish to jeopardize the base metal underneath the anodic layer. Having said that, what is a stripper bath comprised of? Is it possible to produce one's own stripping solution in house? Does anyone care to share a recipe for such a bath? Secondly, what proprietary chemicals or solutions should be considered at the same time?

That takes care of the stripping question but this fellow would also like to have what some people refer to as a "splash effect" produced on his marker. For those who do not know what I am referring to, splashing is produced my literally splashing a masking agent onto the aluminum prior to coloring. This produces an interesting splatter look on the colored surface once the part has been colored and the masking agent has been removed. This brings me to masking agents.

Does anyone know of any proprietary masking agents available on the market. I have done some looking but have been unable to produce satisfactory results. Or is it possible to produce one's own masking agent in house?

Thanks in advance for your responses.

Daniel DeGueldre
anodizing shop entrepreneur - Ste. Anne, Manitoba, Canada
2004

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Dan,

A bath that won't harm the substrate contains Chromic acid, and Nitric acid, and water. This bath is heated to approx. 170 F. I doubt you want to mess with this, as it opens a can of regulatory/safety worms that you probably aren't prepared to deal with. As far as a "splash" look, one way to accomplish this cheaply is to anodize the whole part, then "splash" some clear nail polish on the part (you may have to dink with the viscosity), let it dry, then go ahead and dye, and seal. Once sealed, remove the nail polish with acetone [on eBay or Amazon], then go ahead and re-seal the gun in order to seal the areas masked off by the nail polish. If you want to splash different colors, Clariant makes products called Aluprints which are available in multiple colors. Warning.. Aluprints are not cheap. While the nail polish thing will work, be warned that its a far cry from using the Aluprints, which don't have to be removed prior to sealing, and are specifically made for what you are trying to do.

Marc Green
anodizer - Boise, Idaho
2004

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2004

You may also want to look at "Fantastic Finish: P.L. Selective redefines the art of aluminum anodizing" in this month's Metal Finishing magazine.

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

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Daniel,

We did some research about how to strip the anodized aluminum. After several tests, we found that we can use stronger hydrofluoric acid, by which I mean, 5 part of HF into 20 part of water. But be careful when you dip the anodized aluminum.

Daniel Herman S Suhendra, drs
- Jakarta, Dki, Indonesia
2004

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