The white metals are a series of often decorative bright metal

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

s used as a base for plated silverware, ornaments or novelties, as well as any of several

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, l ...

-based or

tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...

-based alloys used for things like bearings,

jewellery Jewellery ( UK) or jewelry (U.S.) consists of decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a western pe ...

, miniature figures,

fusible plug A fusible plug is a threaded cylinder of metal usually of bronze, brass or gunmetal, with a tapered hole drilled completely through its length. This hole is sealed with a metal of low melting point that flows away if a pre-determined, high tempe ...

s, some

medal A medal or medallion is a small portable artistic object, a thin disc, normally of metal, carrying a design, usually on both sides. They typically have a commemorative purpose of some kind, and many are presented as awards. They may be int ...

s and metal type. The term is also used in the antiques trade for an item suspected of being silver, but not hallmarked. A white metal alloy may include antimony,

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs na ...

, and

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic ta ...

(some of which are quite toxic). Not all of these

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typica ...

s are found in all white metal alloys. Metals are mixed to achieve a desired goal or need. As an example, a base metal for jewellery needs to be

castable In materials science, a refractory material or refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycrystalline, polyphase, ...

, polishable, have good flow characteristics, have the ability to cast fine detail without an excessive amount of

porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

and cast at between .

Silver

In compliance with British law, the British fine art trade uses the term "white metal" in auction catalogues to describe foreign silver items which do not carry British Assay Office

hallmarks A hallmark is an official mark or series of marks struck on items made of metal, mostly to certify the content of noble metals—such as platinum, gold, silver and in some nations, palladium. In a more general sense, the term ''hallmark'' can al ...

, but which are nonetheless understood to be silver and are priced accordingly.

Tin-lead and tin-copper alloys

Tin-lead and tin- copper alloys such as

Babbitt metal Babbitt metal or bearing metal is any of several alloys used for the bearing surface in a plain bearing. The original Babbitt alloy was invented in 1839 by Isaac Babbitt in Taunton, Massachusetts, United States. He disclosed one of his alloy rec ...

. have a low melting point, which is ideal for use as

solder Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitabl ...

, but these alloys also have ideal characteristics for

plain bearing A plain bearing, or more commonly sliding contact bearing and slide bearing (in railroading sometimes called a solid bearing, journal bearing, or friction bearing), is the simplest type of bearing, comprising just a bearing surface and no rolli ...

s. Most importantly for bearings, the material should be hard and wear-resistant and have a low coefficient of friction. It must also be shock-resistant, tough and sufficiently ductile to allow for slight misalignment prior to running-in. Pure metals are soft, tough and ductile with a high coefficient of friction.

Intermetallic An intermetallic (also called an intermetallic compound, intermetallic alloy, ordered intermetallic alloy, and a long-range-ordered alloy) is a type of metallic alloy that forms an ordered solid-state compound between two or more metallic eleme ...

compounds are hard and wear-resistant but brittle. By themselves, these do not make ideal bearing materials. Alloys consist of small particles of a hard compound embedded in the tough, ductile background of a solid solution. In service the latter can wear away slightly, leaving the hard compound to carry the load. This wear also provides channels to allow in

lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, ...

(

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

s). All bearing metals contain antimony (Sb), which forms hard cubic crystals.

References

{{DEFAULTSORT:White Metal Alloys Bearings (mechanical)

Silver

Tin-lead and tin-copper alloys

See also

References