Precious Metals and Alloys

Precious metals and precious alloys are rare metallic elements and alloys such as silver, gold, platinum, palladium, iridium, osmium, rhodium, and ruthenium. They are durable, extremely resistant to corrosion and oxidation, and of high economic value. Precious metals and alloys have higher melting points than other metals. Metallic elements such as silver and gold are internationally recognized forms of currency under ISO 4217 from the International Standards Organization (ISO). Precious metal alloys are used in decorative, dental and industrial applications.

Silver, gold, platinum, and palladium are well known precious metals and precious alloys. Silver (Ag) is a white, malleable, and very expandable metallic element that is soluble in nitric and hot sulphuric acid. Silver is resistant to alkalis in its melted state and generally found in rare ores. Gold (Au) is a soft metal with a characteristic yellowish color and sheen. Gold is found in naturally-occurring veins and in alluvial deposits. Platinum (Pt) is a silvery-white metal that is both malleable and ductile. Platinum is found uncombined in alluvial deposits, and is prepared commercially as a by-product of nickel-refining from copper-nickel ores. Palladium (Pd) is a lustrous, silver-white metal with a face-centered cubic crystalline structure. Precious mnetals and alloys such as palladium can be used to form many compounds and several complex salts. They have a great ability to absorb hydrogen.

Precious metals and precious alloys include iridium, osmium, rhodium, and ruthenium. Iridium (Ir) is a white, shiny metal that is similar to platinum, but very hard and brittle with a melting point of 2454° C. Iridium is often added to platinum for improved hardness and resistance. Osmium (Os) is a lustrous, bluish-white, extremely hard metal that has a pungent smell. Osmium is almost entirely used to produce very hard alloys for instrument pivots, needles and electrical contacts. Rhodium (Rh) is a lustrous, silvery, hard metal, which is used as a hardener for platinum and palladium in order to produce alloys used for electrodes, furnace windings, crucibles, and thermocouple elements. Ruthenium (Ru) is a hard, lustrous, white metal that does not tarnish at room temperature. Ruthenium can be used as a versatile catalyst, such as to split hydrogen sulfide. Other precious metals and alloys also have special properties.

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• AN0011 Solder Alloy Choice and Stress Release Cracking in Through Hole Ceramic Capacitors
  It has been well known for a number of years that solder alloy choice is a critical factor in soldering to ceramic discoidal and planar array capacitors. The introduction of lead free solder alloys as...
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