Organic Deposits on Precious Metal Contacts

An amorphous brownish organic deposit has been found on non-arcing palladium contacts. It is shown that this material is produced when a number of metals, notably those of the palladium and platinum groups, are rubbed together in the presence of low concentrations of organic rapors. The deposit is given by a very wide variety of organic materials, and is thought first to involve chemisorption of the vapor on the metal, followed by frictional activation and polymerization of the chemisorbed layers to form the visible accumulation. The use of a gold alloy overlay on the palladium to minimize the troublesome effects of the polymer on contact performance is discussed.