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Removal of Cloisonne by Chemical Stripping
Q. I am in the automobile restoration business and would like to know what the chemical is that is used in the removal of cloisonne, so that my company can repair medallions and name plates to have the cloisonne replaced. I have heard to use hydrofluoric acid, nitric acid, and fluoboric acid. The glass needs to be removed from the medallions or nameplates, however the piece itself must be unharmed from the removal process. Any guidance would be appreciated to help keep these rolling pieces of history looking like new.
Joe Cahillclassic/antique automobile restoration - Ogdensburg, New Jersey
2006
A. These acids suggest you wish to dissolve the enamel or glass and keep the wire frames. Correct?
Is copper wire used in these? If so, I suggest concentrated hydrofluoric acid with the addition of an inhibitor. Azole compounds (mercaptobenzothiazole (MBT), benzotriazole
[on
eBay or
Amazon]
, tolytriazole) offer some protection to copper.
--- ASM Metals Handbook Vol. 13 'CORROSION'
[affil link
on Amazon], p. 497. You can also contact 'Chemicals' suppliers below for pickling inhibitors (more commonly used with sulfuric or hydrochloric acids).
Use appropriate safety precautions with the very dangerous HF. It should be as concentrated as possible (49 wt% -- anhydrous gas would be better but is more dangerous). Avoid using nitric acid or any other oxidizer with copper. Probably use a plastic container inside a larger container with a lid. Hold parts in a perforated plastic (e.g., polypropylene) dipping basket -- try
'Equipment' link below.
Hope this helps; I had never heard of cloisonnes.
- Goleta, California
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