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Brown sludge in cadmium cyanide plating solution

October 19, 2009

I have a cadmium plating solution that has started to precipitate out a light brown fine sludge onto the bottom of the tank and on the cadmium anode balls.
It is now starting to impact on plating times, the bath is run in a jobbing style shop, i.e. non automated doing aerospace work.
The solution although old has been maintained throughout its life with weekly analysis
with component concentrations at:-
Cadmium 20.0 g/l
Cyanide 109 g/l
Hydroxide 11.8 g/l
Is it just a matter of filtering out the solid, or a sign of something more serious?
I have consulted the Canning Handbook, it has nothing to say about this phenomenom.

Mark Lees
chemist - Isle of man United Kingdom

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