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 pinkis ...

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, where

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 ...

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 wit ...

, 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

latten Historically, the term "latten" referred loosely to the copper alloys such as brass or bronze that appeared in the Middle Ages and through to the late-18th and early-19th centuries. Such alloys were used for monumental brasses, in decorative effect ...

s 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

and

copper alloy Copper alloys are metal alloys that have copper as their principal component. They have high resistance against corrosion. The best known traditional types are bronze, where tin is a significant addition, and brass, using zinc instead. Both of t ...

compositions loosely grouped into the categories: copper, high copper alloy,

es, bronzes,

copper nickel Cupronickel or copper-nickel (CuNi) is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. The copper content typically varies from 60 to 90 percent. (Monel is a nickel-copper alloy that contains a minim ...

s, copper–nickel–zinc (nickel silver),

leaded copper Leaded copper is a metal alloy of copper with lead. A small amount of lead makes the copper easier to machine. Alloys with a larger amount of lead are used for bearings. Brass and bronze alloys of copper may have lead added and are then also someti ...

, 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. Section 23 2D CU-SI

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 *

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 UNS C69100, also known as Tungum alloy, CW700R and CZ127, is a bronze copper alloy. It has a naturally occurring oxide layer, which on exposure to reagents develops into a very thin protective coating. Tungum resists both pitting and crevice c ...

Precious metal alloys

Copper is often alloyed with precious metals 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 met ...

(Au) and

silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...

(Ag). † amount unspecified

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