Metal on Electroplating

What kind/types of metal does not produces solder in electroplating?

In electroplating Sn/Pb ( rack plating ), basically we are using racks which compose of contact pins which connect from the strip frame. As far as I know, the type of metal that the contact pin is steel. Is this right? Anyway, this pins produces solder on their outer layer. The more solder it produces, the less current is applied. So, we are adjusting the specified parameter to achieve the required thickness. Another problem I can ask is the inconsistency of plating thickness. How can we maintain the 300 - 600 micro-inch thickness? Going back to my query, is there another kind of metal in such a way do not produce solder or if none, any metal produce only minimal solder?

Hoping for your kind consideration and understanding...

If I understand correctly, the solder (pb/sn) build-up is normal, the pins on the rack are in conductive circuit with the part. Try stripping the racks after each production cycle. If you don't, the contacts (or pins) will build-up more and more, thus requiring more current.