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topic 59027

Excess sodium cyanide in copper cyanide electroplating solution

November 5, 2012

Q. Dear Sir
I wrongly added excess sodium cyanide in copper cyanide electroplating solution; now instead of copper plating there are bubbles evolving on cathode (the item being plated). Please resolve my problem.

Susheel Daga
- Jodhpur, Rajasthan, India

November 7, 2012

A. 1. For cyanide copper plating solution, copper cyanide forms a complex with sodium cyanide; whatever balance is free cyanide. An addition of copper cyanide will reduce your free cyanide content.
2. Hydrogen bubbling at the cathode is a natural occurrence in cyanide copper plating -- what's the problem?

SK Cheah
- Penang, Malaysia

December 3, 2012

A. Please advise what the analysis is now and what it is normally run at.
As Mr. Cheah advised, each Kg of copper cyanide requires 1.1 Kg of sodium cyanide to dissolve it, so each Kg of copper cyanide will lower the free by 1.1 Kg.
However, if the metal content is already high or the free cyanide is very high as indicated by the excessive gassing then we need to know the concentrations to give better advice.

Geoffrey Whitelaw
Geoffrey Whitelaw
- Port Melbourne, Australia

December 10, 2012

A. Well it is a little excessive but I have done it before. A little diluted 34% hydrogen peroxide will get rid of that problem right away. Just be very, very careful adding it as it will jump right back out at you. Very nasty but works.

Trent Kaufman
Trent Kaufman
   electroplater - Galva, Illinois

December , 2012

A. Second warning on the "be very, very careful" note. That sounds like pretty much the same ingredients as the notorious "jewelry bombing" mix. Yes, I could see it jumping back at you.


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Ted Mooney, P.E.
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