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Copper alloys are metal
alloys 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, ...
that have
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
as their principal component. They have high resistance against
corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
. The best known traditional types are
bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids suc ...
, where tin is a significant addition, and
brass Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other wi ...
, using
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 periodi ...
instead. Both of these are imprecise terms, having both been commonly referred to as lattens in the past. Today the term ''copper alloy'' tends to be substituted, especially by museums.British Museum, "Scope Note" for "copper alloy"
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Composition

The similarity in external appearance of the various alloys, along with the different combinations of elements used when making each alloy, can lead to confusion when categorizing the different compositions. There are as many as 400 different
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
and copper alloy compositions loosely grouped into the categories: copper, high copper alloy,
brass Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other wi ...
es,
bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids suc ...
s, copper nickels, copper–nickel–zinc (nickel silver), leaded copper, and special alloys. The following table lists the principal alloying element for four of the more common types used in modern industry, along with the name for each type. Historical types, such as those that characterize the
Bronze Age The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...
, are vaguer as the mixtures were generally variable. The following table outlines the chemical composition of various grades of copper alloys.


Brasses

A brass is an alloy of copper with zinc. Brasses are usually yellow in colour. The zinc content can vary between few % to about 40%; as long as it is kept under 15%, it does not markedly decrease corrosion resistance of copper. Brasses can be sensitive to
selective leaching In metallurgy, selective leaching, also called dealloying, demetalification, parting and selective corrosion, is a corrosion type in some solid solution alloys, when in suitable conditions a component of the alloys is preferentially leached from ...
corrosion under certain conditions, when zinc is leached from the alloy (''dezincification''), leaving behind a spongy copper structure. * Nordic Gold


Bronzes

A bronze is an alloy of copper and other metals, most often tin, but also aluminium and silicon. * Aluminium bronzes are alloys of copper and aluminium. The content of aluminium ranges mostly between 5% and 11%. Iron, nickel, manganese and silicon are sometimes added. They have higher strength and corrosion resistance than other bronzes, especially in marine environment, and have low reactivity to sulphur compounds. Aluminium forms a thin passivation layer on the surface of the metal. *
Bell metal Bell metal or bell bronze is an alloy used for making bells and related instruments, such as cymbals. It is a form of bronze with a higher tin content, usually in approximately a 4:1 ratio of copper to tin (typically, 78% copper, 22% tin by mas ...
*
Phosphor bronze Phosphor bronze is a member of the family of copper alloys. It is composed of copper that is alloyed with 0.5–11% of tin and 0.01–0.35% phosphorus, and may contain other elements to confer specific properties (e.g. lead at 0.5–3.0% to form ...
* Nickel bronzes, e.g. nickel silver and cupronickel *
Speculum metal Speculum metal is a mixture of around two-thirds copper and one-third tin, making a white brittle alloy that can be polished to make a highly reflective surface. It was used historically to make different kinds of mirrors from personal grooming ...
* UNS C69100


Precious metal alloys

Copper is often alloyed with
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lu ...
s like
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
(Au) and
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
(Ag). † amount unspecified


See also

* Copper-clad steel *
Copper alloys in aquaculture Copper alloys are important netting materials in aquaculture (the farming of aquatic organisms including fish farming). Various other materials including nylon, polyester, polypropylene, polyethylene, plastic-coated welded wire, rubber, pat ...
*
Antimicrobial copper-alloy touch surfaces Antimicrobial copper-alloy touch surfaces can prevent frequently touched surfaces from serving as reservoirs for the spread of pathogenic microbes. This is especially true in healthcare facilities, where harmful viruses, bacteria, and fungi coloni ...
* Lubaloy C41100


References


Bibliography

* {{cite book , first1=Erik , last1=Oberg , first2=Franklin D. , last2=Jones , first3=Holbrook L. , last3=Horton , year=1992 , title=Machinery's Handbook , edition=24 , page=501 , publisher=Industrial Press Inc , location=New York , isbn=0-8311-2492-X


External links


Corrosion tests and standards: application and interpretationCopper Development Association
*Copper Binary Phase Diagrams generation code (batch file - http://www.gotrawama.eu/copperNIMS/ramefabio.txt ) using open thermodynamic databases available at NIMS https://cpddb.nims.go.jp/cpddb/periodic.htm and a commercial software, Computherm Pandat, available for free at https://computherm.com/ ( help for use https://computherm.com/docs/pandat_manual.pdf. Images of the 34 binary phase diagrams are available at http://www.gotrawama.eu/copperNIMS/PNG/ Copper alloys, Sculpture materials