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topic 0116

Shelf life of chromic acid anodize coating

A discussion started in 1995 and continuing through 2008.
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We have an application that calls for unsealed chromic acid anodize as the surface preparation for 6061T6 aluminum. Normally a corrosion inhibiting primer would be applied immediately after the anodize, but for this application the customer has requested that no primer be used. My question is; what is the shelf life of unsealed chromic acid anodize, when it is used as a surface preparation for a structural adhesive bond? I have checked the sources available to me, and have been unable to find a quotable reference. Thank you in advance for whatever assistance you can offer.

Ken W [last name deleted for privacy by Editor]

Surface Treatment & Finishing of Aluminium and Its Alloys
Wernick, Pinner & Sheasby
from Abe Books


Handbook of Aluminum Bonding Technology and Data
from Abe Books



Dear Sirs,

Besides anodize bath conc. , bath temp. and plating current density, is there any other process parameter control on phosphoric acid anodize bath? What is the Al content control for the anodize process ?

Thank you for the reply.

T F Chao
- Singapore

November 8, 2008

Hi, Ken. Sorry, I'm not familiar with a shelf life limit for chromic acid anodize. Hopefully you'll get some additional input from other readers.

Hi, T.F. You can go by D3933-98 [link by ed. to spec at TechStreet]. Additionally there is a Boeing spec for phosphoric acid anodizing, BAC5555. I don't happen to have a copy, but it may contain the parameter information you are looking for.


Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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