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Want Cyanide Free Gold Strip Bath

Q. We are looking for a non-CN stripping solution to strip gold. In our "perfect" world it would be safe for aluminum, stainless steel and copper. I am open to any suggestions at this point though.

Chris Rossiter
- Hayward, California, USA

A. If your base metals are copper based you can try sulfuric acid-glycerol based formulations or sulfuric acid-copper sulphate [this product on eBay or Amazon affil links] formulations.


Venkat Raja
- Kitchener, Ontario, Canada

An acid Thiourea [this product on eBay or Amazon affil links] process was patented in 1986 and has been used in many parts of the world. It however is not the perfect stripper for you as it also strips copper. It is also used to strip silver on semiconductor packages prior to solder plating. In this case the copper is brightened without substantial removal. Also used in the jewelry industry after precious metal casting for brightening and deoxidizing the parts.

gwynne edson
Gwynne I Edson
- Huntington Beach, California

Multiple threads merged: please forgive chronology errors :-)

Q. We are currently investigating the possibilities of eliminating all uses of cyanide from our plating processes. The major stumbling block we have found is finding a cyanide free gold strip solution. We selectively plate electroless copper and nickel on plastic and use an immersion gold process on some parts. Occasionally, we need to rework parts and strip inadvertently plated barrels. While we have been able to identify several non-cyanide gold immersion baths, it has proven difficult to find a cyanide free method of stripping gold from these items.

Brian DeBadts
- Rochester, New York

A. These can be used for Au removal: Aqua regia (3HCL:1HNO3) Aqua regia will etch just about every other metal, too.
Tri-iodide: 400 g KI, 200 g I2, 1000 ml H20. There are other more exotic mixtures, but these are the most common non cyanide ones in use.

Tom Hand
- Woburn, Massachusetts

Multiple threads merged: please forgive chronology errors :-)

Stripping gold from copper and nickel substrates

Q. Hello everyone, been a long time since I posted here , I have a customer looking to strip gold from copper substrate , and wants to know if it can be done without cyanide?
Any input, especially some old school solutions are what I'm looking for.

Ron Landrette
plating equipment supplier - Bristol, Connecticut
April 24, 2008

A. I think the most convenient procedure might depend on your particular situation, this is, how much gold you got in the material and the total amount of it. Maybe you want to recover the gold from old electronic components There are plenty of studies for precious metal recovery from electronic scrap. I suggest to start with a web-search. The following paper might help:

"The aqueous recovery of gold from electronic scrap "
JOM Journal of the Minerals, Metals and Materials Society
Volume 55, Number 8 August 2003

Good luck,

Manuel Sández
University of Sonora - Hermosillo, Son. Mexico
May 15, 2008

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