We use a copper cyanide plating bath that is “housed” in a steel tank. In the last three or four weeks, copper has started to deposit on the walls of the tank. What is happening and how can we eliminate the problem? C. S.
The problem you are suffering with is stray currents. Stray currents are hard to pin down and certainly have led to many grey hairs for electroplaters. One possible cause is that your parts near the bottom of the tank may be closer to the bottom than to the anodes. Another cause may be “stray parts” that have fallen off your racks and are now at the bottom of the tank.
Switching to a lined tank can minimize the problem. Other things you can do are to clean out the tank on a regular basis and to pay closer attention to the racking and positioning of your parts when in the plating tank. I like to call these two suggestions “paying attention to the details!”