Question:
We use a cyanide copper strike with stainless steel anodes. The bath is operated at 4.0 oz/gal copper, 2.0 oz/gal free cyanide and a pH of 12.5–13.5. The stainless steel anodes form a dark film after a day or two of use and the plating solution turns a dark yellow. R. A.
Answer:
Your problem lies with the stainless steel anodes. The highly alkaline plating solution will dissolve chromium from the stainless steel anodes and cause the filming of the anodes and the deep yellow color of the plating solution. A better choice of anodes is cold-rolled steel. Keep in mind that one of the standard methods for stripping chromium from steel substrates is an alkaline solution with the parts to be stripped being made anodic. This essentially is what is happening in your cyanide copper plating bath.
