Inventors:
William Kono - Albany NY
John P. Nielsen - New York NY
International Classification:
C22C 506
C22C 508
Abstract:
Sulfide tarnish inhibiting of silver base alloys selected from the group consisting of Ag-Cu, Ag-Au, and Ag-Cu-Au is achieved by adding to silver base alloys at least one element with passivating ability and with heat of sulfide formation which exceeds the heat of sulfide formation of silver and in the amount which does not exceed 1. 5 weight % as substitute of silver, so as to form a thin layer of oxide of the element which is selected from the group consisting of Cr, Ta, Al, Ti and Th. The layer of oxide is thin and does not affect the properties of silver base alloys. The added element, in the event of damage to the oxide layer, forms a sulfide film of the element before formation of silver sulfide, to thereby protect silver base alloys from tarnishing.
