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Electroplating gold onto copper without gold solution

April 23, 2009

I'm a mariner here in Western Australia and I enjoy making small marine decorative parts (bosun's pipes, paraffin lamps etc). I have a number of small copper items which I would like to gold plate for decorative, non-electrical purposes. I have bits of scrap gold metal suitable for use as anodes. And I have a variable current/voltage DC regulated supply. I'm armed with a rusty but workable chemistry knowledge. And time is not an issue. SO...

Do I have to purchase gold solution from jewellers' suppliers, or is there some way I can electrolyse my scrap gold metal directly into solution (say a dilute HCl/H2O solution) and then reduce the Au+ out of the solution onto the copper (either in 1 step or several). Alternatively can I formulate my own gold solution some other way without using cyanide or aqua regia- both of which I cannot legally obtain (and wouldn't want to work with anyway) ?

Any hints on the surface areas ratios and the emf/amperage required to say lay down 1 gram of gold on 10 cm sq. of copper ?

Johnson Kitto
home craftsman - Perth, WA, Australia

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April 25, 2009

DIY cyanide free gold plating solutions:
2,65 gm gold chloride
15 gm potassium ferrocyanide ⇦ this on eBay or Amazon [affil links] (0-5-1% of potassium cyanide based bath)
15 gm sodium carbonate ⇦ this on eBay or Amazon]
1 lit water
ss anodes,2 V
Bath II
1 gm gold chloride
75 gm sodium phosphate
2,5 gm sodium sulphite
1 lit water
ss anodes
You can even make your own gold chloride -dissolve gold scrap in aqua regia-heat obtained solution(very slow) until it is very thick and sirupy and then you can add it to bath.More infos on ferrocyanide bath can be found in Precious metal plating book by J.Fischer and D.E.Weimer (Teddington 1964.)
At www.uspto.gov website you can find some expired cyanide free gold plating patents too(one sodium thiosulphate ⇦ this on eBay or Amazon [affil links] based, and one tartrate based). Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia