Contamination in Nickel Tank

Q. We are doing nickel electroforming on copper molds. Before plating, we etch the copper molds using phosphoric acid. We have discovered that we have phosphorus contamination in our nickel plating solution. Is there a way to remove this contamination? K.P.

A. I am not aware of any method that can be used to remove the phosphorus contamination from your plating bath. Perhaps one of our readers has a suggestion for doing this. In the meantime, I would investigate why you are getting this dragout from your phosphoric acid cleaning and etching step. My bet is that you aren’t doing thorough-enough rinsing prior to placing the parts in the nickel plating solution.
Why are you using copper mandrels? Typically mandrels are made of inert materials or materials that are easily dissolved after the electroforming process is completed. In recent years, aluminum has become a favorite for mandrels.