The Influence Of The Corrosive Atmosphere On The Common Contact Metals

The electric contact is widely used in communication and electronic industry, so its reliability is very important. The capability of contact material is the final factor on ability of electric switch and reliability of contact. Environmental pollution is very serious in China, the common corrosive gases are SO₂,NO₂ and Cl₂ and so on. Under the effect of the polluted gases, the corrosion films of the metallic contacts of the components are produced, so the contact resistance of contact points will rise and the reliability of the related electric equipment will be reduced. Therefore, it is very useful to research the influences of the corrosion films on contact behavior.The main content of this paper is to study the influences of SO₂ and NO₂ to the common metal material Cu and Ni, including the compare and analysis of the representational methods for corrosive gas SO₂ and NO₂, the morphology,composition and electric contact performance of the corrosion films.Through the compare of the standards ISO,HNO₃ and JIS, the maneuverability of the standard JIS is better than ISO and HNO₃. High corrosive acids are used in the standard ISO and HNO₃; and perfect protected measures are necessary during the experimental process. SO₂ concentration in the standard ISO is much higher than that in the standard JIS.The corrosion films are analysed after corrosion experiments, including themorphology, composition and electric contact behavior. The corrosion films formed on metal surface have two types: one is oxide, which covers the whole sample suefaceand the height is much less. The others are gibbosities, which are corroded more serious than oxide. Electric contact performance of corrosion products shows three following types: first, static and dynamic resistances are all very high and even reach the given "open" value; second, static resistances are open but dynamic resistances can fall to several mΩafter some frettingcycles; third, static resistances are mensurable and dynamic resistances can fall to several mΩafter some frettingcycles.In addition, the corrosions products formed on gold plated sample have the same composition as that formed on Ni sufuace, so gold plated sample can be replaced by pure substrate metal sample. The changes of humidity are not the only factor for the formation of corrosion rings through experiment.