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  for Metal Finishing since 1989
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Conversion coatings on aluminum

1997

Where do I find information about conversion coatings on aluminum. I want to replace the native oxide with a surface alloy or something else that is a better electronic conductor than the initial surface oxide so that I can electroplate onto aluminum foil

Any suggestions ?

Robert A. Huggins Chr. Albrechts University, Kiel, Germany

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Conductivity may not exactly be the question: it's possible to phosphoric acid anodize and then electroplate.

But the most conventional way of plating onto aluminum is to do a 'zincate' pretreatment, which consists of immersing the article in a highly caustic zinc-rich solution, stripping in nitric acid, and repeating. Look up 'zincate' in the guidebooks for further detail or inquire of Atotech regarding their proprietary alternative 'Alstan', or Canning-Gumm Chemical [now Macdermid] for their proprietary alternative 'Bondal'.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
1997

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1997

Chemicals solutions to produce chromate conversion coatings on aluminum are sold by a number of companies worldwide. One of these manufacturers is probably your best source for technical information. The US Dept. of Defense maintains a long list of products approved to meet the military specification (QPL-81706 [on DLA]). Two of the most widely recognized are Alodine(R) by Parker Amchem [now Henkel] and Iridite(R) by Macdermid. In fact, these brand names are often used generically when referring to chemical conversion coatings.

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.

Wadsworth, Ohio

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Conversion coating on aluminum and plating on aluminum are two different things. Ted recommended a process for plating and Chris for conversion. They do not go together, if you apply a chromate film you cannot plate on it only paint it.

Sara Michaeli
Tel-Aviv-Yafo, Israel
1997