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Stripped and re-anodized parts are grey instead of clear

My name is Daniel and looking for some help on anodizing. I have some type 2 anodize parts that need to be reworked. I want to strip the anodize off and re anodize type 2 .0003-.0007 I tried one stripped it and it came out dull of the anodize tank. I glass beaded it tried it again and same problem. The original finish was a nice clear coat, but now the finish is coming out a dark grey any one help me with this problem

Daniel Macin
plating shop - Tempe
February 16, 2011

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Since the anodic oxide is 1/2 under the original surface and 1/2 on top of the original surface, you will NEVER get back to the same luster. You may limit the roughing of the strip by using the phosphoric/chromic formula for panel stripping that is in the Mil Spec, or come back and we will list it for you. Again, after the no-attack stripping, you still will not get back to what you had before you converted the original surface to aluminum oxide.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

February 17, 2011

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Daniel, you will probably need to know what aluminum alloy your parts are made of. Electrochemical polishing the items prior to anodizing should limit the articles turning grey. It is also important to note that the racking of the parts is such that they do not go loose during the process.
Again, glass beading or sand blasting only helps to make the surface greyer after the anodizing. Electropolishing goes a long way in giving luster to the article prior to anodizing. The luster should remain and the parts should remain silverish up to an anodizing coating of 30 microns.
Hope this helps.

Winston D'Souza
- Bombay. India
February 20, 2011