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"Alodine compositional changes in service"

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2002

Would Alodine undergo any sort of change when exposed to the following conditions:

A 3003 aluminum battery terminal is coated with Alodine. This terminal is in contact with a nickel plated copper bar that is coated with a tin/lead solder (50-70% tin by weight, Mil-P-81728). (The interface with the Alodine surface is the solder). A current of 54A is passed through the interface. Can that amount of current affect the composition/integrity/characteristics of the Alodine? Are there any special cleaning techniques needed for the aluminum prior to Alodine coating (other than alcohol cleaning)?

Thank you

Cacey Jennings
- Palo Alto, California USA

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2002

Alodine is a trade name for a product for chromate conversion coating of aluminum, Cacey, so you would want advice from the particular supplier. But two things sound wrong here: first, alcohol cleaning is not usually considered adequate pretreatment for chromate conversion coating of aluminum; second, I am surprised that chromate conversion coating would be considered an adequate treatment for aluminum for a high current low voltage application like this--I would have expected electroless nickel on an application like this.

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