Behavior of Contact Surfaces Consisting of Gold Alloys in H2S-NO2-SO2Atmospheres

Tests Carried out in connection with a project for ensuring suitable test atmospheres for precious-metal contacts are reported. The contact resistance behavior of Au alloys is described after exposure in a flowing atmosphere of cleaned air mixed with the aggressive gases H2S, NO2, and SO2at concentrations between 0.4 and 4.0 ppm. By means of a regression calculation the influences of the different gas components are determined. In addition to the electrical measurements the chemical compositions of the tarnish layers were analyzed by SIMS.