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Letter 068
Copper sulphate crystals in plating tanks
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I read that copper plating solutions should last for years with
proper maintenance. In my solution which I used for about a month, I
had about a 1/2 inch thick chunk of blue crystals in the bottom of my
tank as well as on the sides and anodes. I assume this is copper
sulfate. Is there any reason this would grow in there? Too much
brightener perhaps? (I added a bit much I think )
Thanks Rob
G. Touch
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There is nothing wrong with the bath. The solution is just
saturated. It has either been made up and used warm, then allowed to
cool beyond solubility, or excess acid in the solution has continued
to dissolve copper from the anodes which has pushed the copper
sulfate beyond the solubility limit. The latter is likely when
vigorous air agitation is left on for long periods. The crystals are
not a problem, unless they start salting out into the deposit. The
best thing to do is analyze the solution, decant to remove excess
copper sulfate, and replace any sulfuric acid and chloride necessary
to return it to the vendor's recommended operating range (assuming
use of a proprietary brightener). Please dispose of all wastes
according to applicable regulations.
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Bill Vins
microwave & cable assemblies
Mesa (what a place-a),
Arizona
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