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Trivalent Chromium Treatment for Aluminum

I am trying to address corrosion problems on my personal aircraft. I recently learned about trivalent chromium alternatives such as Aluminescent to products such as Alodine. First, literature for tri hex indicates that certain PH levels must be maintained. How critical is this, and does mixing the correct proportions achieve the correct PH? I can add acids or bases, but this is more complicated than I want to get. I will be brushing or spraying, so contamination of the mix will not be a problem. Second, is the mix stable over time, i.e. can I mix up a few gallons and store sealed for extended periods? Third, how do you find a distributor who is willing to work with a personal purchase. Suppliers seem to only want to work with other companies. I am willing to purchase powdered quantities sufficient to make about a hundred of gallons of mix. Do I need to tell them this up front?

Jason Bowman
consumer and hobbyist - Bellbrook, Ohio, USA
2007

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First of two simultaneous responses --

The technical data sheet should specify how pH is to be attained, monitored, and maintained for the particular process but, yes, there is a good possibility that simply making up the mix will deliver the right pH.

Inorganic chemicals like chromates are usually quite stable and I think I recall a couple of letters on line here where very old chromates proved to be workable.

Indeed, companies are often unwilling to sell industrial chemicals to consumers, not just due to volume but as part of their responsible stewardship as well. If you are cynical about associating the word 'responsible' with corporations, you could probably say that in a society that repeatedly proves itself guilty of always assigning the blame to the entity with the deepest pockets, deep pocket companies simply can't afford the risk of selling to consumers :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

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Second of two simultaneous responses --

Try www.uspto.gov website(patents database) - there you can find some simple solutions(tannic acid ⇦this on eBay or Amazon [affil links] based).Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia
2007

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One of the companies who supplies a formulation based on NAVAIR's TCP is Metalast. Should they be unwilling to supply an individual, they have at least one plating shop they supply (and we use) within a day's drive of Bellbrook. Perhaps that might be a way of getting your parts coated.

Another place to try is Wright Pat AFB. They certainly have an active interest in investigating trivalent chromate processes for aluminum, and may be able to assist or advise.

Good luck!

Lee Gearhart
metallurgist - E. Aurora, New York
2007