Metal finishing Q&As since 1989

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Chemically Polishing Aluminum

Hello,

I have been searching for an chemical aluminum polishing solution on the internet for a few days now, and can not seem to find a site that fully explains the ins and outs of the different methods. From what I have read, the bright dip may be the best option, but again I can not seem to find a distributor who sells the solution for aluminum.

I am also wanting to find out about the container requirements, maintenance, safety equipment and such, but have only found spotty information here and there. There are some messages on this board, but none that answer all my questions.

Seeing as how I am new to chemical polishing (but not to anodizing or dealing with chemicals) I would like to have some specifics on set-up and use of the products.

Thanks and God Bless,

Scott Gunnell
Plating shop - Watauga, Texas, United States
2004

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First of three simultaneous responses --

What you want is known as R-5 bright dip (nitric and phosphoric acid mixture). It does a good job brightening aluminum. It's also mean stuff, runs very hot and lots of fumes. You should be able to find a reference and formulation in any good handbook on Al finishing.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2004

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Second of three simultaneous responses -- 2004

If you run or work in a plating shop you should have a good plating book like the Metal Finishing Guidebook and Directory issue. There are three baths listed there for bright dipping aluminum as follows:

1-Tragacant gum 0.5-1 oz/gal, HF acid 4.5-5%v, room temp (mix gum w/alcohol to paste, add to hot water, let cool to room, add the acid), maintain with additions of HF.

2-Hydrofluosilicic acid 4%v, wetting agent(like Nacconol) 0.1 oz/gal, room temp., maintain w/addition H2SiF6.

3-Phosphoric acid 80%v, Nitric acid 5%v, acetic acid [on eBay or Amazon] 5%v, rest water, temp 220oF, no maintenance dump when not effective.

Guillermo Marrufo
Monterrey, NL, Mexico

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Third of three simultaneous responses -- 2004

Check with the local suppliers here in the area. I think they can get you a bright dip for Aluminum. I used one a few years ago and it did brighten somewhat, depending on the alloy. The Metal Finishing Guidebook also has some info on different formulas.

Jim Conner
Anoplex Software

Mabank, Texas USA