Silver Migration in Electrical Insulation

Silver migration may be defined as a process by which silver, when in contact with insulating materials under electrical potential, is removed ionically from its initial location, and is redeposited as metal at some other location. This process requires adsorption of water on the insulation surface. Silver is unique in this respect in that it is easily oxidized and reduced and does not passivate. Other metals do not present a practical migration hazard. Presented herein are examples of actual experience wherein silver migration caused trouble, and an explanation of this phenomenon based upon chemical and physical considerations and related laboratory evidence. It is concluded that silver should be used with great caution under the conditions noted.