Where’s My Silver?

Question:

We specialize in the plating of silver on electrical components used in the electric industry. We do both rack and barrel plating. We have been tracking the amount of silver anodes consumed versus the amount of silver deposited on our parts and seem to be losing approximately 10% of the silver. Over a year’s time this is a rather large dollar amount. Do you have any suggestions on how we can reduce our loss of silver? C.O.

Answer:

Silver is one of those metals that has been known to have a rather high vapor pressure at times (tends to vaporize out of the plating shop). Assuming this is not the issue, I would start by looking at the dragout in your plating processes. Each time a rack or barrel is removed from the silver plating tank, some of the plating solution adheres to the surface of the parts, the racks or the barrels. This solution must be returned to the plating tanks.

To start with, are you allowing a long enough drain time before going into the rinsing process? How are the parts racked? If possible, the parts should be racked in such a way that the dragout can consolidate and drain from a single or at most a couple of points. In your barrel plating operation you want to be sure that they are not overloaded. Overloaded barrels tend to drain poorly. Use of misting can also help here.

The rinsing part of the plating process should also be investigated. Some of the silver plating solution will end up in the rinse water. This silver that is present as a silver cyanide complex should be recovered. A silver specific ion-exchange system can help you here.

Silver can be lost by plating out on racks and danglers. Strip your racks on a regular schedule. Filters can also “trap” some silver. The used filter media should be returned to your precious metal refiner for silver recovery.