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Help with carbonate build up in Albaloy bath

October 28, 2008

Hi,
We are having a problem with carbonates building up to fast in our Albaloy bath.The bath is a potassium cyanide based bath. I know carbonate build up is a natural thing but, I was wondering if there is a way to slow down the process or even remove some of the carbonates.We keep the pH at 13, the temp at 140 degrees, and the potassium cyanide level between 9 and 10 oz/gal. The MAX limit for carbonates is 10 oz/gal.The bath solution becomes cloudy the closer it gets to the limit. Then we decant about 20% of the bath and replace with DI water. After that the bath solution clears up, we run a lab analysis, make the adds to bring bath back into spec. Bath is good for about two weeks, then we do it again.The 20% we decant is sent out as hazardous waste and this becoming expensive.
Is anybody elsle having the same problems with their Albaloy bath? Any suggestions are welcomed.

Jerry Hannibal
plating shop employee - Beverly, Massachusetts, USA

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November 4, 2008

Cyanide plating baths from carbonate complexes from the breakdown of the cyanides. Therefore, this is always going to happen to a greater or lesser extent. Some ways that accelerate this process are: air agitation or any form of agitation which causes air to be entrained in the solution i.e. barrel rotation, filter discharge, air leak in filter, etc. Further, at 140 deg F. you are also breaking down cyanide due to temperature.

You should first look to see if you can minimize any of the above. Then look at your heating. If you are maintaining 140 deg F. check to make sure your control is properly calibrated and you are not exceeding this temperature. Then make sure that there is adequate solution movement near the heating device to eliminate localized overheating.

You can chemically remove the carbonates, however that is probably just as costly (materials, labor, disposal, downtime) as what you are doing now.

Gene Packman
process supplier - Great Neck, New York

To reduce carbonate and keep the solution loss at a minimum you can also use a freezing out process. If you use Potassium based salts the freezing out process will be limited.

Dominik Michalek
- Mexico City, Mexico
November 6, 2008