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Incomplete Anodize Finish and Surface Imperfections

I'm having a problem with a couple of my aluminum parts. The parts as received have incomplete coverage as well as white streaks.
Tech info:
Material - AMS4027M
Processing Specs:
ANODIZE PARTS PER AMS2471.
PROCESS COMPLETION PERMITTED PER MIL-DTL-5541 [on DLA] CL-1A OR AMS2473 .

Scott Haenel
manufacturing engineer - Dayton, Ohio
December 23, 2008

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Mil-DTL-5541 is a chromate conversion specification, and depending on the type/class a yellow, streaky, non-uniform surface is normal with this finish.

Ryan Cook
Toccoa, Georgia
January 5, 2009

Thanks, is there anyway to achieve a more uniform finish? I'm receiving rejection notices for UVC.

Scott Haenel
manufacturing engineer - Dayton, Ohio
January 7, 2009

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January 8, 2009

Scott

You should be able to expect either, or both finishes, to be consistent in appearance on your material (6061-T6). If your part receives both processes, chem film, (mask) and clear anodize, failure to completely remove the chem film in the subsequent cleaning operation will result in white/milky/frosty flaws in the anodize.

A check of the anodize thickness in the suspected areas might be appropriate.

Willie Alexander
- Colorado Springs, Colorado