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Sealing Hard Coat: nickel acetate vs. hot DI

We anodize aluminum gun parts 7075 and 6061 mostly. Most of the work is dyed black. I have been asked to evaluate the advantages of hot DI seal versus nickel acetate. Anyone with experience sealing with both mediums would be very helpful. A large concern is the ascetics of the parts.

Ken Clay
employee - Tucson, Arizona
March 3, 2009

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First of two simultaneous responses --

You'll definitely want to use nickel acetate for sealing dyed parts. I believe the seal quality is better with a boiling DI seal, however, dyes tend to leach out in in the bath, contaminating the DI water very quickly.

Also, boiling DI seal tanks are expensive to operate due to the continuous electricity needed to keep them at temperature, while a lot of nickel acetate baths operate around 165 F. Constant ph monitoring is also necessary with boiling DI tanks as they tend to drift more than the nickel acetate baths.

Finally, since you mentioned ascetics... when using boiling DI, you'll get the un-wanted "bloom" on the parts which can be labor intensive to remove.

Marc Green
anodizer - Boise, Idaho
March 5, 2009

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Second of two simultaneous responses --

Dyed anodic coatings should always be sealed in nickel acetate. Hot water seal is only acceptable for non-dyed, indoor exposure.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

March 5, 2009