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Removing nickel cyanide from silver plating bath

We have just recently installed a new silver plating line and while running this solution with scrap components have generated the complex nickel tetra cyanide. I would like to know can this complex be removed safely from solution via adding another reagent? What are the long term implications to our silver strike and silver plating solution if levels continue to rise? Is there an acceptable level of nickel tetracyanide allowed in solution? We ARE NOT using silver anodes but Stainless Steel grade 316.

Nigel D Gill,B.Sc.MIMF AIEMA
Technologist - Glasgow, South Lanarkshire, Scotland
2004

It is a strange coincidence that I was working on a possible solution to that problem just today. I am a retired consulting chemist with more than 25 years in Ag plating and Ag chemistry.

One likely source for the Ni is your Ag Strike with the 316 anodes due to high anode current density. If you go directly to the plating bath without a rinse, then that Ni will build up from both drag-in and the SS Anodes in the plating bath. If you can increase your anode area in your Strike easily, it will reduce the amount of Ni entering the bath. If not, perhaps a change of anode material would help. Is there a reason you cannot use Ag anodes in the plating bath

Since you obviously add AgCN to make up your deposited Ag, my suggestion is that you could try dummying some of your solution in your lab, using Pure Ag anodes onto a weighed Stainless plate. The theoretical deposition potential of Ag(CN)2- is very close to that Of Ni++ in the equilibrium Ni2(CN)4 = Ni++ + Ni(CN)4--. Analyze the solution before and after plating as well as the weighed deposit for Ag and Ni and do a mass balance at several current densities. If there is Ni depositing with the Ag This will show you a way to reduce the Ni in your solution and also tell you that Ni is co-depositing in your electroplate. Not knowing your application or additives I hope these thoughts are of some value to you.

Thomas L. Faudree III
- Danbury, Wisconsin
2004

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Have you had any luck with removing Ni from your Ag Bath?

I would be very interested in your results, should you be able to disclose them.

Thomas L. Faudree III
- Webb Lake, Wisconsin
2004