Surface films on precious-metal contacts

A study of the incidence and behaviour of thin films on platinum-metal surfaces has been carried out by measuring contact resistance at loadings from 1 mg to 5000 mg. It is shown that reproducible results can be obtained, corresponding to film thicknesses of the order of 5 A. Surface properties appear to be more sensitive to the mode of preparation and the subsequent treatment than to the identity of the platinum metal. Abrasion leads to a progressive deterioration at light loads, whereas surfaces produced by breaking sintered compacts, by cold-forming, and by electrodeposition remain essentially stable over periods of months.