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Removing copper from acid copper tank

 

Our acid copper plating tank (sulfuric acid/copper sulphate) has crept up in copper content aver the past two years and it needs lowering (30g/l down to 17g/l). The reason was believed to caused from excessive anode corrosion, as we used non-phosphorized anodes and were they un-bagged (bad news).

Dilution would seem like the obvious way to reduce copper levels but, I have been thinking of a different approch. Is it common practice to plate out the copper with an inert electrode? Possibly using Pb sheets or nobal metal mesh electrodes. The copper "anodes" in the bath would become a cathode. In this way no waste is generated. Acid would increase slightly but that is not a concern.

Adam Seychell
- Melbourne, Australia

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Hi Adam,

Many customers in the Rotogravure industry use Pb sheet (in place of some Cu anode area) to reduce the Cu content without affecting the quality of the deposit. The only thing I would mention is that because of evolution of oxygen at the anode, a slight acid Cu mist may irritate some of the operators. A simple shroud should keep the mist down.

Anode bags and filtration should be used in most applications to prevent surface roughness. It has to be noted that P/Cu (0.02-0.04%P) will dissolve in a more uniform manner. P Cu also has a slight polarisation of 0.5V.

Regards,

Jonathan Timms
- Hong Kong