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Zirconization of anodized aluminum

Q. I have an aluminum extruded bowl that has been sulfuric acid anodized per Mil-PRF-8625F, Type II, Class 1, thickness- 0.002mm to 0.025mm, natural color. The anodizing is sealed with a nickel acetate. The part is going to be subjected to a Zirconization process. Will this make the surface suitable for paint adhesion?

Timothy Barr
Project Engineer - Bethlehem
July 1, 2025

A. Hi Timothy

The ideal surface treatment of aluminum which will be painted or powder coated is chromate conversion coating or trivalent chromate conversion coating per Mil-C-5541. Anodizing, especially sealed anodizing, is a poor surface for paint or powder coating adhesion. Zirconization of anodized and sealed aluminum as a paint bonding pretreatment would be a special case I wouldn't want to guess about. If these are existing parts which must be reworked, I think you need to ask DuBois or your distributor for advice regarding what they have learned about Zirconization of sealed anodized aluminum.

If they are new parts I think you'll save money & processing time, and obtain a better product, by chromate conversion coating the raw aluminum bowls and forgetting the anodizing.

Luck & Regards,

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

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