Dummy plating - Remove metal contaminants using low current density

A. Low current density treatment works in certain cases but not for all metallic contaminants in all kinds of plating solutions. It depends on certain curves that have been developed empirically that establish ranges of current densities in which each metallic ion plates preferentially in presence of other ions for a given solution.

A. Hi,
As previously stated not all metallic contaminants plate out. Whether they can or can't is explained by their position in a table known as the electrochemical series.
It is probably easiest to take a practical situation of say, copper in nickel plating baths.
Contrary to the popular view, copper will plate out preferentially to nickel at all current densities. However, the only metal ions that can be plated out are those at the cathode surface. At HCD the metal plated will be predominantly nickel simply because the low concentration of copper is rapidly depleted. As the CD becomes lower, there is more time to replenish the copper and it's concentration in the deposit rises. Finally at very LCD the deposit becomes copper rich. So, the amount of nickel wasted in the dummying process is kept to a minimum. One very important point in dummying is to have good agitation so that the copper is continuously and rapidly brought to the dummy sheet surface.
Is this of help?

Hey THANKS all of you! Yeah, it helps a lot!

Harry,
I appreciate your excellent explanation. I had a vague and inexact idea. Thanks,

A. Hi Koh. I think it's simply "the electrochemical series", or a table of "half-cell voltages". You'll instantly see a hundred such charts if you google it. Good luck.

Regards,