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Pure Gold is besides Platinum the chemically most stable of all precious metals. In its pure form it is not very suitable for use as a contact material in electromechanical devices because of its tendency to stick and cold-weld at even low contact forces. In addition it is not hard or strong enough to resist mechanical wear and exhibits high materials losses under electrical arcing loads. This limits its use in form of thin electroplated or vacuum deposited layers.
For most electrical contact applications gold alloys are used. Depending on the alloying metal the melting is performed either under in a reducing atmosphere or in a vacuum. The choice of alloying metals depends on the intended use of the resulting contact material. The binary Au alloys with typically <10 wt% of other precious metals such as Pt, Pd, or Ag or non-precious metals like Ni, Co, and Cu are the more commonly used ones ''(Table 2.2)''. On one hand these alloy additions improve the mechanical strength and electrical switching properties but on the other hand reduce the electrical conductivity and chemical corrosion resistance ''(Fig. 2.2) '' to varying degrees.
[[File:Physical Properties of Gold and Gold-Alloys.jpg|right|thumb|Physical Properties of Gold and Gold-Alloys]]
[[File:Influence of 1-10 atomic of different.jpg|right|thumb|Influence of 1-10 atomic% of different alloying metals on the electrical resistivity of gold (according to J. O. Linde)]]
Under the aspect of reducing the gold content ternary alloys with a gold contentof approximately 70 wt% and additions of Ag and Cu or Ag and Ni resp., forexample AuAg25Cu5 or AuAg20Cu10 are used which exhibit for manyapplications good mechanical stability while at the same time have sufficientresistance against the formation of corrosion layers ''(Table 2.3)''. Other ternaryalloys based on the AuAg system are AuAg26Ni3 and AuAg25Pt6. These alloysare mechanically similar to the AuAgCu alloys but have significantly higheroxidation resistance at elevated temperatures ''(Table 2.4)''.
Caused by higher gold prices over the past years the development of alloys with
Table 2.1: Commonly Used Grades of Gold
[[File:Phase diagram of goldplatinum.jpg|right|thumb|Phase diagram of goldplatinum]]
