Letter 7051

Iron contaminated Cobalt Hardened Gold Plating Bath  

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I am trying to remove Iron from a potassium cyanide gold citrate based plating solution. The bath has a gold content of 4 g/l with a pH of 4.2 - 4.6 and a cobalt content of 300 - 500 mg/L. The bath has a Iron content of 200 mg/L and it is causing a problem as to meeting a purity of deposit spec. The Iron is being plating out in a matter of 0.298% in deposit. I have tried a variety of resins but to no success.

The Iron has to be possibly lowered to 25 - 35 mg/L to pass our purity of deposit spec.

Is there a chemical treatment process which will not remove all of the Gold and most of the iron. Dummy plating is not an option.

Doug Duda
Uyemura Technical Center - Southington, CT. 06489

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