Metal finishing Q&As since 1989

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copper sulphate crystals in plating tanks

1995

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 sulphate. 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 sulphate [on eBay or Amazon]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 sulphate, 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.      

Bill Vins
microwave & cable assemblies - Mesa (what a place-a), Arizona
1995