Letter 27077

Can I anodize on top of existing anodic film [New Zealand] 

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Hi There,

I have a component that has already been anodized,type ii sulphuric. The material is 6063. My question being, I have had some rework performed,and would like to anodize the re-worked areas. Can I just anodize the whole thing again,on top of the old anodizing? Or will I have to strip the old anodizing off and start again.

ps, Masking the old anodizing is not a practicle solution.

Thankyou for time Regards,

Steve Power
Helicopter Engineer - Nelson, SI, New Zealand

NO !!!

For example, Type II anodizing is used as a maskant for Type III selective anodizing.

You can take a part out and look at it, keep it wet, and restart anodizing, but once it starts sealing (even in cold rinse water) there is NO re-starting.

Robert H Probert Robert H Probert Technical Services Garner, NC, USA Editor's note:        Mr. Probert is the    author of Aluminum How-To

steve,

the anodizing will only 'take' on bare/de-oxidized surfaces. just be careful that during the process, the existing anodizing is not chemically removed. why not just strip and anodize again? tolerances? surely that's the safest?

Michael Georgiadis
fishing reels - durban, south africa

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