Silver palladium alloy

by: Davitz, Daniel;

A silver colored metal alloy having improved tarnish resistance is disclosed, which is intended primarily for solid sterling jewelry and utensils and may also be used in silver plating, and does not easily tarnish and corrode. The alloy consists essentially of 80% to 92.5% silver, 4% to 9% palladium, 0% to 10% copper and 0.5% to 1% indium or zinc.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to silver alloys, and in particular to a silver alloy having improved tarnish resistance. Sterling silver ordinarily alloy contains 92.5% silver, and 7.5% copper. Preferably this alloy must be moldable and castable with low surface tension to conform to intricate molds. In addition, the alloy should provide a material which does not easily tarnish and corrode, especially when used for jewelry.

2. Prior Art

Sterling silvery jewelry and utensils are valued because of their intrinsic worth and the silver color of the metal. However, a problem has been found in using sterling silver because of its tendency to tarnish and corrode.

Many attempts have been made to improve the tarnish and corrosion resistance of sterling silver and to improve the casting qualities of sterling silver.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a more corrosion resistant and tarnish resistant silver alloy with better working properties then sterling silver.

For example, an alloy called premium has been provided in the past which comprises 74% A.sub.g, 25% Pd 1% ZN. Another alloy previously sold is 66% A.sub.g, 23% Pd, 10% Cu and 1% ZN. However, these alloys have been found to be more expensive and thus have not found substantial commercial use.

Accordingly, an object of the present invention is a silver alloy having chemical and physical properties suitable for use in jewelry.

An additional object of the present invention is to provide a silver color alloy, that will have better tarnish, an corrosion resistance with excellent working properties and still have a low cost alloy.

Other objects of the present invention and advantages accruing therefrom will be apparent to one skilled in the art in the following detailed description. all percentages referred to ar percent by weight based on the total weight of the material or mixture.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the present invention, a silver colored metal alloy is disclosed which is exceptionally tarnish resistant and corrosion resistant and comprises the following ingredients: 80% to 92.5% silver, 4% to 9% palladium, 10% to 0% copper and 1% to 0.5% indium or zinc.









To be considered in the sterling family, an alloy must have at least 92.5% silver. Usually the remainder of the alloy sterling silver is copper and sometimes zinc. In the present invention, we have replaced most or all the copper with palladium to enhance tarnish resistance and corrosion resistance. We find that this not only gives us a more color stable alloy then sterling silver, but also due to the addition of indium and palladium, the working and casting properties are much improved and the alloy is not brittle. The ratio of silver preferred due to cost and to be considered like sterling silver is 92.5% silver, 5% palladium, 2% copper and 0.5% indium or zinc.

Palladium in this alloy gives the alloy a much greater tarnish and corrosion resistance.

The use of copper enhances the working properties when in conjunction with the pal adium and silver.

The specific gravity of this alloy is 10.27 gms/cc plus or minus, 0.5. Other physical properties are as follows:

    ______________________________________
    Low Hardness         105 BRINELL
    High Hardness        165 BRINELL
    Elongation           15 to 26%
    ______________________________________


Specifically, the preferred alloy formula in accordance with this invention is:

    ______________________________________
    Palladium        5%
    Silver            92.5%
    Copper           2%
    Indium (or zinc)   .5%
    ______________________________________


While the specific alloy described is intended primarily for solid sterling jewelry and utensils, it may also be used in silver plating using conventional silver plating techniques. As a result, a highly tarnish resistant silver plate is provided at a nominal increase in cost.

The above described alloys have a casting temperature of approximately 1850 degrees Fahrenheit plus or minus 50 degrees. The melting temperature of the alloys is approximately 1750 degrees Fahrenheit plus or minus 50 degrees.

Conventional chlorine and/or ammonia testing of this alloy exhibits n tarnishing or corrosion after exposure for 10 days. While this invention has been described with reference to a preferred content and formula, it will be understood by those skilled in the art that various changes may be made and equivalents substituted for elements described herein without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the scope thereof. Therefore it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Non-aqueous electrochemical cell

Variable delay memory system

Catalyzed fluorination of chlorocarbons

Fermentation process

Froth flotation

Golf putt training apparatus

Internal combustion engine

Output regulator

Wheelchair motorizing apparatus

Method of treating melanoma

Portable foldable splint

Front vehicle body structure

Pulse width modulation operation circuit

Process for decoking catalysts

Perfusive chromatography

Paint toning machine

Thermosensitive recording sheet

Three dimensional space viewing device

Modular station platform construction kit

Master cylinder apparatus

Insulating insert for magnetic valves

Preparation of 2-amino-4-fluoropyrimidine derivatives

Heterocyclic-methylene-penems

Asymmetric wire rope isolator

Cervical traction device

Low-noise frequency synthesizer

Expandable tire building former

Electromechanical preparation of photoengraving cylinders

Polishing apparatus

Medical garment

Optical fiber strain relief device

Flash memory device

Layered film and packaging material

Fast circuit switching system

Electronic voting machine

Direct conversion receiver per-selection

Phosphorus-containing copolyamides and fibers thereof

Multiple unit cigarette package

Metering apparatus

Fuel system

Motor vehicle wiper

Door clip

Vertical storage toolbox

Tricyclic amides

Fuel system for multicylinder engines

Power-generating control apparatus for vehicle

Splash guard

Powder dividing device for camera

Screw

Brake pressure control valve

Pharmaceutically active morpholinol

Ice body delivery apparatus

Compartmentalized basket truck

Lime sludge press unit

Fishing hooking device

Ion-channel forming peptides

Depth-resolved fluorescence instrument

Magnetic blanket for horses

Shutter time control circuit

Nitrogen detection

Drum construction

Inter-LAN connection method using ISDN

Aerobic exercise device

Security and deployment assembly

Environmentally stable monolithic Mach-Zehnder device

Stabilized throttle control system

Endoscope signal level control

Wearable display

Motor control system

Control means for ground hydrants

Simultaneous telecommunication between radio stations

Magnetic domain propagation register

Method of preparing ferroelectric ceramics

Imidazodiazepine derivative

Digital character display

Surface modifier composition

Passive lavatory cleanser dispensing system

Production of dihydroxydiphenyl alkanes

Naso-gastric tube retainer

Solar thermal propulsion unit

Developing unit for electro-photographic apparatus

Towable "V" rake agricultural machine

Facsimile compression for transmission

Motor vehicle gearbox

Structurally efficient inflatable protective device

Modular nuclear fuel assembly design

Polysaccharides and preparation thereof

Sliding exhaust brake system

Clothes hanger

Incontinence electrode apparatus

Valve timing adjusting device

Collapsible wheelbarrow

Dual chamber water filter

Isothiazole and isoxazole sulphoxides

Automatic reversal mechanism

Automatic trimming machine

Triarylpropyl-azabicyclooctanes

Movement detector

Fuel dispensing nozzle

Method of fabricating electronic circuits

Drain-extended MOS ESD protection structure