The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Gold electroforming bath composition

Can anyone give me the best formula for gold electroforming to give more than 1000 microns? I have gold electroforming solution bath from citric acid and potassium citrate, and p gold cyanide and cobalt sulphate and indium sulphate but very bad in thickness

Majed Janineh
silver electroforming - Beith Lehem Israel
September 18, 2011

---

September 21, 2011

The bath you have sounds like a typical acid gold hardened with cobalt and indium. These baths are mainly used for electronics applications on wear surfaces such as circuit board fingers and connector pins. The deposits from these are much more stressed than pure gold deposits and I can't imagine that bath being used for electroforming. At some thickness, I would think that you will experience stress cracking. Also, these baths are generally only about 30-40% efficient. To summarize, I think you have the wrong bath.

About 40 years ago, I worked for a company than made high purity gold and silver electroformed slip rings. For the gold ones, grooves were machined into a plastic cylinder and were filled with electroformed gold. I don't remember the thickness but it was at least as thick as what you need. It's been a long time, but the alkaline cyanide bath used was about 100 liters, or more, and contained 32 g/l of gold as PGC plus potassium cyanide and potassium carbonate. Fairly standard old hi-gold content, heated cyanide gold bath.

You could also use a low stress proprietary sulfite gold bath to plate that thickness.

Chris Owen
- Nevada, Missouri, USA