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world gathers for metal finishing
Q&As since 1989


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Hard Anodize

I was wondering if you might be able to answer a question for me. Is it necessary to leave portions of the metal containing solution in the tank when re-charging. Or,is it advisable to do a complete recharghe? I am referring to Hard Anodize. Your help is appreciated,

Lewis Marsh
1999

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Recommendations by experts in literature are to have at least 4 g/l dissolved aluminum in an anodizing bath. Baths with little or no dissoved aluminum are supposedly more prone to burning parts, and Al dissolution during anodization is much faster than in baths containing 4-20 g/l aluminum. Faster Al dissolution can lead to a more porous anodize. Baths can run as high as 20 g/l Al, but for more consistency in the anodize some shops dump at 12 g/l or even lower levels. I have run hardcoat baths both ways, but usually used new baths with caution. If you need to dump completely for tank cleanout or to eliminate other contaminants or for other reasons, run less critical parts in a new bath until the Al level builds up.

Phil Johnson
- Madison Heights, Michigan
1999

Is it possible to safely perform hard anodizing on small parts in my garage? What do I need? Are there starter kits available? Where can I get the necessary components?

James E. Ellis
- Tempe, Arizona
2000