Film formation on silver-based switching contacts

The reactions of atmospheric pollutants with silver-based switching contact materials produce corrosion products which can adversely affect the contact's electrical behavior. In the present study, three silver-based contact materials-Ag/Cu/Ni, Ag/Ni, and Ag/MgO/NiO-were exposed to an accelerated corrosion environment containing SO/sub 2/, H/sub 2/S, NO/sub 2/, and Cl/sub 2/. An elevated temperature and high humidity were also maintained. Both electrical degradation and corrosion film growth characteristics were studied as functions of exposure time. It was found that contact resistance increases rapidly with the initial corrosion film formation, silver chlorides and silver sulfides are the major corrosion products formed in the accelerated aging environment, and corrosion film thickness and uniformity have strong effects on contact resistance.<>