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Anodize Agitation

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I have a question regarding the placement of air agitation in a chromic acid anodize tank. Should the air move up between the cathodes and the parts, or directly up across the parts? I am getting conflicting answers from, what I consider, reliable sources.

David Glassner
- Vandalia, Ohio, USA

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First of two simultaneous responses -- +

I believe that air agitation is primarily for cooling. As long as there is sufficient and continuous heat exchange between the solution and the cooling coils, the location of the air agitation will not matter.

Dado Macapagal
- Toronto, Ont

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Second of two simultaneous responses -- +

Hi Dave,

Good to see you in this forum. I think ideally you would want moderate to strong agitation over the entire tank surface. But if I had my choice I would want it coming up directly on the parts. Air agitation performs many functions, but one of the most important is to prevent parts from burning by insuring fresh solution contact. Drop me a line sometime.

Rick Richardson, MSF Techmetals Inc. Dayton, Ohio

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I would not use air in a chromic anodize tank for 3 reasons. First, air will cause mist which is a health and safety issue if not completely controlled by fume extraction. Second, even if the mist is extracted, the chrome concentration may overcome the ability of the scrubber to remove it. Third, we are supposed to control fumes by addition of a foaming agent which builds a foam blanket on the top of the tank. The use of air disturbs the blanket and causes more emissions.

Instead of air agitation, we use pumps and eductors to move the acid.

Jeff Pernick IHC Inc - Detroit, Michigan