Letter 3004

Treatment of Acid Gold Cyanide Baths 

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Hi. I'm trying to gather information on treating acid gold cyanide baths. I work in a reel to reel shop. We use cobalt hardened acid gold cyanide baths for gold plating. These baths initially are a purple color attributable to the cobalt brightner (I believe Cobalt (+2) EDTA). Over time the baths develop a straw brown color. My best guess (from talking to others on this subject) is that the cobalt is gradually converted to Cobalt (+3) Cyanide. There is a treatment process for gold baths which I have learned about. Although the exact procedure and interpretation of the purpose varies significantly depending on who you're talking to. The process involves heating the bath, adding H2O2, adding EDTA, carbon treating, adding free cyanide. I'm hoping some of you can supply me with some information on this procedure.

JD Kronicz
- Hanover, PA

Why do you want to treat the bath? If there is a quality issue, it makes sense (e.g. deposit hardness out of limits, brightness gone, etc.). If you just like the color of a new bath forget it! On the other hand, if the bath performance has deteriorated, check with the supplier. They are the ones who will know what to do. If you screw up a gold bath it's a pretty expensive mistake. I would certanly want the vendor on my side!

Bill Vins microwave & cable assemblies Mesa (what a place-a), Arizona

Can somebody please tell what precautions to take while working on acidic gold cyanide baths specially against HCN gas liberated during plating. Also please tell how to detect that HCN gas in surroundings is exceding the maximum safety amounts.

Thanks........

Aashish Agrawal
- MUMBAI, MAHARSHTRA, INDIA

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