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Black anodizing is velvety, and discolors when touched

Q. Hello, I am having issues with my black dyed anodising. When it is removed from the hot water seal and dried, it has a velvety look to it. When I touch it, it leaves finger prints, and when I take a thickness reading with my DFT meter, the point where I take the reading goes a strange greenish colour. Please help!

Gillian Tracey
Employee - Coleraine, Co.Antrim, N.Ireland
February 18, 2016

A. First you have an anodizing problem, come back with alloy, prep-process, free acid, temp, and current density.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

March 16, 2016

A. Sounds to me as if you're seeing seal smut. For dyed work, try using a mid-temp nickel acetate seal.

Marc Green
anodizer - Boise, Idaho
March 17, 2016

A. Gillian

The cause could be either anodize step or seal step related. To help determine, blow dry the surface of a couple of parts immediately prior to sealing and examine.

Willie Alexander
- Colorado Springs, Colorado
March 17, 2016

A. Good day Gillian.

I do not know the depth of your experience, but there is good info at
diyanodizing.com
like anodizing basics/dyeing.

Hope this helps.

Regards,

Eric Bogner, Lab. Tech
Aerotek Mfg. Ltd. - Whitby, Ontario, Canada
March 17, 2016

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