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How to get gold plating of at least 5 microns

I don't seem to be able to get a straight answer from my supplier. I'm currently using a cyanide based gold plating solution. This is one of the common solutions used in the Jewellery business. I'm gold plating base metal rings and I cannot get a thick coat of gold deposit on the items. The directions for the plating bath are the following:
Heat at 130-140 F and plate with 5-6 Volts for about 15-30 seconds, using a Stainless Steel anode.
By doing that I only get a flash and sometimes when I lightly buff the piece with a cloth the plating goes away. I tried to lower the voltage to 2.5-3 Voltage and increase the plating time to about 1.5-2 minutes. The same happens. And when I plate for about 5 minutes the plating becomes too dull and dark.
Another company sells a K24 gold plating solution that according to what they say it will plate 2 microns in 2 minutes. And if I need to pate thicker just leave it longer and than wipe the piece to remove the dull finish. I don't know if I can trust this.

Any ideas? I need to have a bright thick gold plating that will last for years. A plating I can engrave on.
Thank you in advance for your time.

Pierre P [surname deleted for privacy by Editor]
Jewellery and watch case plater and refinisher - Montreal, Quebec, Canada
September 12, 2008

The company that told you they have a gold bath that will plate 2 microns (over 80 microinches) in 2 minutes was in error, unless the gold concentration of the bath is way up there, and who can afford that nowadays. Secondly, the bath you are using now is made for what you say, "a flash coating". The bath could also be low in gold. The deposit should not just rub off, even at 5-7 microinches thickness. Why do you want to plate 2 microns of gold on jewelry? If you want a thicker deposit you will have to increase the gold concentration and other constituents in the bath. You could plate 25 microinches max if you want a quality product. You will have to sell the rings for a lot more though because you are putting on almost 5X the amount of gold than the average jewelry plater. Good Luck!

Mark Baker
process engineer - Malone, New York
September 17, 2008