Solving The Air Pocket Problem

Ask an Expert From: Products Finishing, from Anodizing Technologies

Posted on: 5/1/2007

Question: We are trying to anodize a round part about 12-inch diameter with deep pockets in about 20 sections like a turbine fin.

Question:

We are trying to anodize a round part about 12-inch diameter with deep pockets in about 20 sections like a turbine fin. We are having problems with air pockets and no anodizing in the pockets. We have tried different ways of racking and also moving the parts back and forth to allow them to fill up with anodizing solution. Any ideas on how to solve this problem? C.J.

Answer:

It’s sort of difficult to solve this problem specifically without actually seeing the parts. I can only offer some fundamental suggestions. Obviously, the parts have to be positioned in such a way that no air can be trapped. Where there is an air pocket there won’t be any anodizing, or at least not very much. This leaves the area of the air pocket unprotected by anodic coating and sometimes it causes the pocket area to be discolored. Even though air agitation of the solution is considered essential during anodizing, you could try turning the agitation way down, or even off, to see if that helps. If you position the part initially to fill up all the potential air pocket areas with solution, have no air introduced into the tank to get trapped in these pockets and have fairly vigorous solution agitation by mechanical means (the acid circulating pump), that may do the trick. Sometimes parts can be drilled to keep air pockets from forming, but it sounds like this may not be one of those parts.


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