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Alternative to sulfuric acid for anodizing aluminum

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Aluminum How-To
"Chromating - Anodizing - Hardcoating"
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Q. Hi.
I have several questions re anodizing aluminum, specifically 6061 alloy.

I have read that borax [affil links] or TSP [trisodium phosphate [on eBay or Amazon]] can be used as an electrolyte. Is this true?

Is there any advantage to using sulfuric acid? I can always use the TSP, and/or borax [affil links] to clean other things.

Wouldn't the TSP serve as an adequate cleaner?

What about plain old salt water?

What is desmut, and is it necessary?

Regarding the power supply, isn't it simply a power vs time thing? With this in mind is longer pickling better or worse for the metal? i.e., is the finish harder, softer, or the same?

Does 3 lb. sheet lead make a good cathode? What would be a good hanger? (Anode)

Jim Agans
roof consulting - Eldersburg, Maryland
2006

A. No, James. It is possible that you are confusing the anodizing of aluminum with decorative anodizing of titanium jewelry. Although anodic current is used in both cases, neither the required procedures nor the resultant anodized surface have much in common.

For aluminum you need the acid, not just a carrier of ions. The acid continuously attacks and dissolves the anodized film, and that is what creates the honeycomb pore structure that absorbs the dye.

Please send the aluminum to an anodizing shop if you need it anodized. If you anodize this material for installation on a customer's roof, you've suddenly become an anodizing business, not just a roofing business -- and you will be shocked at the number of permits and licenses you require, the time it takes to comply, and the costs of non-compliance because you will be in a business that generates regulated hazardous waste.

Good luck.

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

Readers may wish to also see:

• Topic 42228 "Anodizing aluminum with formic or citric acid "

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