Changes

For lower electrical loads mainly high precious materials based on Au and Pt are used because of their high corrosion resistance, the latter materials however used only in limited quantities because of the high price of platinum metals. Ag based materials cover the medium load range and are alloyed with Pd for currents <1A and voltages > 24V, and for loads above these levels Ag composite materials with additions of Ni, or the metal oxides SnO₂, ZnO, or CdO are used. While the Pd addition reduces the silver sulfide formation in sulfur containing environments, adding metal oxides increases the resistance against welding and arc erosion at higher make currents. At high switching currents and switching frequency tungsten containing contacts are used, mainly as switching pre-contacts which absorb the electrical arcs at high make and break currents