Letter 11057

Electroplating gold onto silver 

I would like to take my old wedding ring (widower now) and electroplate a silver bracelet. I had thought this would be as easy as determining a conductive solution, hooking a battery anode to the gold and the cathode to the bracelet and sit back and wait. Is this wrong?

Aaron Morris
- Marietta, GA

We'll bite our tongue and not ask why your ring holds so little value to you that you'd throw it away this way. But you need more than a conductive solution, you need a solution that can support the dissolution of gold ions--you can't ionically transport them unless you can dissolve them. Thus, things like vinegar and salt won't work.

As far as I know, you'd need either a cyanide-based solution (forget that idea) or an aqua regia solution (forget that idea) or a special solution with strong proprietary complexors. And there's more to it than ionically dissolving the gold, too--brighteners, alloying metals, the need for a strike bath first, activation of the silver, etc., etc.

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

So what is the answer to the question? I am making a solid silver chess set and would like to plate one side of the set with gold and the other with palladium. Instead of a solution, where the actual gold content cannot be assessed, I was under the impression that I could essentially use a weighed strip or coin of gold in a solution and through the anode/cathode method transfer the gold to the set.My set will have 6.6 pounds of silver and incorporate precious and semi-precious stones when finished, which is why I would like to say that X amount of precious metal was incorporated in its creation.

I have proper hazmat credentials and respirators as well as means of hazmat disposal if that's what it takes to do the job. The will is there...I need the method. Any suggestions?

Ted Wyman
- Fort Worth, TX, USA

Mr. Wyman, you are building a beautiful chess set and the answer is to send it to a plating shop.

The most basic problem is that electroplating is a very difficult, multistep, industrial process. Smarter men than me have written that "Electroplating is probably one of the most complex unit operations known because of the unusually large number of critical elementary phenomena or process steps which control the overall process." People spend their whole lives in electroplating and learn only a small piece of it; entire aisles of technical libraries are filled with books about electroplating.

But people, possibly misled by an experiment from chemistry class, want to do this complex industrial process in their kitchen. And they want to add options that the experienced industrialist wouldn't dream of, like using a wedding band or coin as the anode instead of electrolytically purified anodes, using a battery as the power source instead of a high quality power supply, and with no pH control, no temperature control, no hull cell analysis, no solution agitation, and no facilities or instrumentation for chemical analysis.

And they want to plate with precious metals, one of the marks of which is that the metals are very difficult to dissolve. If you can't dissolve the metal into solution, you can't plate it out of solution. And the chemicals you need to dissolve it are impractical for various reasons--it is impossible to plate out of aqua regia; no responsible supplier will sell cyanide to an individual consumer for shipment to a home; suppliers who have developed specialty sulfite-citrate baths after years of research will not give you the synthesis procedures to manufacture it.

And they want to deposit a thickness that can't easily be achieved in the most advanced laboratory, or deposit heavy layers of a metal (palladium, for example) that is just barely doable at thicknesses of millionths of an inch only with exotic patented chemistry :-)

Real plating is done from proprietary solutions with proprietary alloying metals, brighteners, levelers, wetting agents, and accelerators. It is done in multiple steps, with one solution for the required gold strike step, and a totally different one for the heavy gold plating. All under careful chemical control and with very limited expectations about plating thicknesses that are possible before stresses, impurities, and solution exhaustion cause trouble.

A plating shop can use an ampere-hour meter to deposit a very specific amount of gold for you. Palladium is not a suitable plating; instead, the other pieces could also be gold plated but then topped with rhodium plating. If you see our "must have" book list and borrow a couple of those books from the library you will see the issues that you are up against. Good luck.

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

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