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Shelf life of chromic acid anodize coating

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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]

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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

The Surface Treatment and Finishing of Aluminium and Its Alloys


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 ASTM D3933 [link is 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.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E.
finishing.com
Brick, New Jersey

Handbook of Aluminum Bonding Technology and Data


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