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Alkaline green gold plating

August 25, 2011

Hi,

I work for a company that makes fine jewelry. Recently, we have had trouble with our green gold electroplating process. We have a precipitate that forms whenever we add silver alloy and when we add gold, it seems to deplete rather rapidly. I obtained the specifications from the company that manufactures the chemicals for the bath and the only glaring discrepancy is that it calls for a pH of 9 to 11 and our pH is around 4 or 5. My supervisor said that the pH is of no consequence and is not the reason for the poor efficiency of our system. Is this true? All the other parameters are within specification.

Thank you.
K

Kyle Cruz
employee - Saint Louis Missouri

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First of two simultaneous responses -- August 26, 2011

A company I once worked for was, at that time, the largest supplier of precious metals plating solutions in the world. One of my duties was to act as head troubleshooter for the plating problems our customers were having. I discovered that about 80% of all plating problems could be solved by simply analyzing all the ingredients, pH, temp., etc., of the solutions, and then adjusting everything to the manufacturer's recommended levels.

I don't know how you could tactfully handle this but, if the operating instructions say to operate the pH between 9 and 11, that's absolutely where it should be operated. The people that developed this solution are infinitely more knowledgeable about it than your supervisor.

Is the bath a cyanide system, a sulfite system, or what? How large is the bath? Can you provide the recommended ranges of all the parameters, as given by the manufacturer, and tell us your most recent analysis of all of the ingredients?

Chris Owen
- Nevada, Missouri, USA

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Second of two simultaneous responses -- August 29, 2011

Dear Cruz,
Honestly Your posting initially made me laugh!
I understand supply houses of plating process manufacturing companies invest a lot of money in R&D and bring out widely accepted processes.
In your case you said that the only discrepancy is pH and that is the major one! Please note that you are using an acid gold process and your friend gave you an additive supposed to be used in an alkaline-cyanide bath (see pH 9-11). That is the reason for precipitation.
I am not allowed to further elaborate in this forum else Ted will say "cut"!!
Regards
Mohan

T.K. Mohan
plating process supplier - Mumbai, India