Why does the pH change in our cyanide copper strike? It doesn’t happen all the time. Is there any way to prevent this from happening? S.C.
The pH change is caused by the poor efficiency of your anodes. You don’t say if you are using any insoluble anodes in the strike bath, but if you are, they have low efficiency compared to soluble anodes. This will cause hydroxide ions to be generated at the anode surface, which in turn will increase the pH of the bath. If your copper anodes develop a passivation film, efficiency will also be reduced, causing the same problem, which is production of hydroxide ions.
This change in pH should be less significant if the plating bath contains a high concentration of tartrates (Rochelle salts).