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Anodizing my polished speaker cabinets turns them gray

I have a set of 2 speakers, made out of AL6063-T5. Small sized ones. I have polished them to a nice mirror like finish, from instructions and advice, learnt in this site. However, I have had very little success in getting the cabinets to stay in the original mirrored condition, after I sent them out for clear anodizing. I have done this for 3 times, with different companies, but my end-results have been not satisfactory. My product has turned light greyish in color.

Is there a process before dipping into anodizing tank, that must be performed first ? Please advice. I have used a clean wool pad to rub out left over green wax, after final polish, pack the cabinets into clean boxes, and sent straight to anodizing shop.

Is it an anodizing fault that is not addressed ? I have managed to find out from the third shop, that they are anodizing at 20 °C.  Thank you in advance for any advice. 

Adrian Chin
Hobby - Georgetown, Penang, Malaysia
2004

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Your mechanical polishing process tends to leave the surface with the same metallic composition that you started with, whereas the anodizer uses a cleaning process and possibly an etching process which dissolves aluminum, leaving copper and silicon and other alloying materials on the surface as a gray smut.

To an extent this can be managed with a desmut step designed to dissolve those contaminants, but anodizing will still interfere with brightness to some extent depending on the alloy. Try to find an anodizing shop who does 'brite dipping' before anodizing. This solution not only smoothes the surface, but dissolves the contaminants, and is used on aluminum reflectors.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004