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topic 20135

Preserving bright copper using benzotriazole solution

Current question and answers:

March 14, 2021 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I found a Copper Development Association article. In the article is the following:

"Chelating Agents. Benzotriazole and other chelating agents interact with copper and its alloys to prevent tarnishing. Chelating agents are preferentially absorbed on the surfaces of the metals and act as an invisible barrier to elements or compounds which might cause corrosion. In this way they protect the metal against oxidants permeating through the coating and continue to protect even after a minor defect has formed in the coating. Chelating agents may be included in the coating formulation or applied as part of a pretreatment procedure."

I am specifically interested in the above process to retard copper corrosion on small exterior copper pieces. I've not been able to find out how to use the agents and if they can be done on a small scale (dip tank) for a craft business. Any suggestions you have would be greatly appreciated.
Thanks

Dave Lindley
- PORTLAND Oregon
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March 2021

A. Hi Dave. Benzotriazole [affil. link to info/product on Amazon] is great stuff, and yes you probably can apply it yourself ... but don't expect anything to be a silver bullet against tarnish and corrosion. For stuff that's going to be outdoors I think you are going to need a brass lacquer or some sort of a clear coat, and it's going to have to be periodically renewed every few years. Benzotriazole is a great pretreatment before the lacquer/clearcoat (please read the rest of this thread for info about that), and you can even buy lacquers like Incralac [affil. link to info/product on Amazon] which include benzotriazole if you want to do it that way -- but a permanently bright untarnished copper without a clearcoat doesn't sound likely to me except in very benign environments.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey




Previous closely related Q&A's starting in:

2003

I create copper sculptures with a bright finish and would like to preserve the brightness by applying benzotriazole, possibly followed by a clear acrylic lacquer. I think dipping in a benzotriazole solution would be the easiest way to provide thorough coverage for these pieces. Would alcohol (methanol?) be the best solvent for this application? What concentration of benzotriazole would give a good level of protection?

Thanks,

Bert Smith
- Austin, Texas


I would agree that immersion is a good method of application. Alcohol is a good solvent. Benzotriazole is water soluble at about 2 percent, and is sometimes used as a treatment for recirculating cooling water at low concentrations. It is soluble in alcohol to 50-75 percent, so that would probably be a good solvent for your application. Normally you should get a technical data sheet as well as an MSDS which should give application help.

However, I think a better approach may be to obtain a proprietary and commercial benzotriazole based corrosion inhibitor product rather than to mix benzotriazole with alcohol yourself. The proprietary process might include wetting agents, stabilizers, anti-fume products, a lacquer or varnish, etc., that makes it a usable end-product without the need to reinvent the process sequence.

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


June 3, 2008

My husband gave me a beautiful 3-tier water fountain for my birthday. I DO NOT like the look of copper with patina. I like it shiny and new. Is there a finish I can apply to the copper, maybe spray on, that would keep it from getting weathered/patina? How often would I need to reapply the product? Thanks!
Melody

Melody Matchett
hobbyist - New Glarus, Wisconsin

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