Gold-silver alloys with good tarnish resistance for the dental art
US4255191A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 20, 1980 |
| Grant date | Mar 10, 1981 |
| Priority date | — |
| Expiry date | Feb 20, 2000 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC22C5/06
- WIPO fieldPharmaceuticals
- WIPO sectorChemistry
Abstract
Gold-silver alloys with good tarnish resistance for the dental art are prepared which, contrary to the known tarnish resistant alloys, still contain copper and thus have a deeper gold color and a high ductility. The alloys contain 33 to 48% gold, 0-5% platinum, 1-10% palladium, 0-0.2% iridium and/or ruthenium, 3-9% copper, 1-6% zinc, 0.5-4% tin and 2.5-10% indium, balance silver, wherein the mass ratio of copper to zinc is between 1:1 and 4:1, the content of copper is not higher than the sum of zinc, tin and indium, the content of palladium is at most three times as great as that of indium and does not exceed the sum of zinc, tin and indium. Under these provisions the copper content is not perceptibly disadvantageous to the resistance to discoloration.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.