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Cupronickel or copper-nickel (CuNi) is an
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, ...
of copper that contains
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
and strengthening elements, such as
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in fr ...
and
manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy u ...
. The copper content typically varies from 60 to 90 percent. (
Monel Monel is a group of alloys of nickel (from 52 to 67%) and copper, with small amounts of iron, manganese, carbon, and silicon. Monel is not a cupronickel alloy because it has less than 60% copper. Stronger than pure nickel, Monel alloys are re ...
is a nickel-copper alloy that contains a minimum of 52 percent nickel.) Despite its high copper content, cupronickel is silver in colour. Cupronickel is highly resistant to corrosion by
salt water Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...
, and is therefore used for piping, heat exchangers and condensers in
seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...
systems, as well as for marine hardware. It is sometimes used for the
propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
s, propeller shafts, and hulls of high-quality
boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inl ...
s. Other uses include military equipment and chemical, petrochemical, and electrical industries. Another common 20th-century use of cupronickel was silver-coloured
coin A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order to ...
s. For this use, the typical alloy has 3:1 copper to nickel ratio, with very small amounts of manganese. In the past, true
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 co ...
coins were debased with cupronickel, such as coins of the
pound sterling Sterling (abbreviation: stg; Other spelling styles, such as STG and Stg, are also seen. ISO code: GBP) is the currency of the United Kingdom and nine of its associated territories. The pound ( sign: £) is the main unit of sterling, and t ...
from 1947 onward having their content replaced.


Name

Aside from ''cupronickel'' and ''copper-nickel'', several other terms have been used to describe the material: the tradenames ''Alpaka'' or ''Alpacca'', ''Argentan Minargent'', the registered French term ''cuivre blanc'', and the romanized
Cantonese Cantonese ( zh, t=廣東話, s=广东话, first=t, cy=Gwóngdūng wá) is a language within the Chinese (Sinitic) branch of the Sino-Tibetan languages originating from the city of Guangzhou (historically known as Canton) and its surrounding ar ...
term ''Paktong'', 白銅 (the French and Cantonese terms both meaning "white copper"); cupronickel is also occasionally referred to as ''hotel silver'', ''plata alemana'' (
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...
for "German silver"), ''German silver'', and ''Chinese silver''.


Applications


Marine engineering

Cupronickel alloys are used for marine applications due to their resistance to seawater
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 engine ...
, good fabricability, and their effectiveness in lowering macrofouling levels. Alloys ranging in composition from 90% Cu–10% Ni to 70% Cu–30% Ni are commonly specified in
heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
or condenser tubes in a wide variety of marine applications. Important marine applications for cupronickel include: *
Shipbuilding Shipbuilding is the construction of ships and other floating vessels. It normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to befo ...
and repair: hulls of boats and ships, seawater cooling, bilge and ballast, sanitary, fire fighting, inert gas, hydraulic and pneumatic chiller systems. *
Desalination plants Desalination is a process that takes away mineral components from saline water. More generally, desalination refers to the removal of salts and minerals from a target substance, as in soil desalination, which is an issue for agriculture. Salt ...
: brine heaters, heat rejection and recovery, and in evaporator tubing. *
Offshore oil Offshore drilling is a mechanical process where a wellbore is drilled below the seabed. It is typically carried out in order to explore for and subsequently extract petroleum that lies in rock formations beneath the seabed. Most commonly, the t ...
and gas platforms and processing and
FPSO A floating production storage and offloading (FPSO) unit is a floating vessel used by the offshore oil and gas industry for the production and processing of hydrocarbons, and for the storage of oil. An FPSO vessel is designed to receive h ...
vessels: systems and splash zone sheathings. *
Power generation Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery (transmission, distribution, etc.) to end users or its storag ...
: steam turbine condensers, oil coolers, auxiliary cooling systems and high pressure pre-heaters at nuclear and fossil fuel power plants. * Seawater system components: condenser and heat exchanger tubes, tubesheets, piping, high pressure systems, fittings, pumps, and water boxes.


Coinage

The successful use of cupronickel in coinage is due to its
corrosion resistance 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 engine ...
,
electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
, durability,
malleability Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
, low
allergy Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermat ...
risk, ease of stamping, antimicrobial properties and
recyclability Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...
. In Europe, Switzerland pioneered the nickel ''billon'' coinage in 1850, with the addition of silver. In 1968, Switzerland adopted the far cheaper 75:25 copper to nickel ratio then being used in Belgium, the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
and Germany. From 1947 to 2012, all "silver" coinage in the UK was made from cupronickel, but from 2012 onwards the two smallest cupronickel denominations were replaced with lower-cost nickel-plated steel coins. In part due to silver hoarding in the Civil War, the United States Mint first used cupronickel for circulating coinage in three-cent pieces starting in 1865, and then for five-cent pieces starting in 1866. Prior to these dates, both denominations had been made only in silver in the United States. Cupronickel is the
cladding Cladding is an outer layer of material covering another. It may refer to the following: * Cladding (boiler), the layer of insulation and outer wrapping around a boiler shell *Cladding (construction), materials applied to the exterior of buildings ...
on either side of United States half-dollars (50¢) since 1971, and all quarters (25¢) and dimes (10¢) made after 1964. Currently, some circulating coins, such as the United States
Jefferson nickel The Jefferson nickel has been the five-cent coin struck by the United States Mint since 1938, when it replaced the Buffalo nickel. From 1938 until 2004, the copper-nickel coin's obverse featured a profile depiction of founding father and third ...
(5¢), the
Swiss franc The Swiss franc is the currency and legal tender of Switzerland and Liechtenstein. It is also legal tender in the Italian exclave of Campione d'Italia which is surrounded by Swiss territory. The Swiss National Bank (SNB) issues banknotes and the fe ...
, and the
South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korean Peninsula and sharing a land border with North Korea. Its western border is formed by the Yellow Sea, while its ea ...
n 500 and 100 won are made of solid cupronickel (75:25 ratio).


Other usage

A
thermocouple A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the ...
junction is formed from a pair of thermocouple conductors such as iron-
constantan Constantan is a proprietary name for a copper–nickel alloy also known as Eureka, Advance, and Ferry. It usually consists of 55% copper and 45% nickel. Its main feature is the low thermal variation of its resistivity, which is constant ...
, copper-constantan or nickel-chromium/nickel-aluminium. The junction may be protected within a sheath of copper, cupronickel or stainless steel. Cupronickel is used in
cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
applications. Its combination of good ductility retention and thermal conductivity at very low temperatures is advantageous for low-temperature processing and storage equipment as well as for heat exchangers at cryogenic plants. Beginning around the turn of the 20th century,
bullet A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. Bullets are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax. Bullets are made in various shapes and co ...
jackets were commonly made from this material. It was soon replaced with
gilding metal Gilding metal is a form of brass (an alloy of copper and zinc) with a much higher copper content than zinc content. Exact figures range from 95% copper and 5% zinc to “8 parts copper to 1 of zinc” (11% zinc) in British Army Dress Regulations. ...
to reduce metal fouling in the bore. Currently, cupronickel and
nickel silver Nickel silver, Maillechort, German silver, Argentan, new silver, nickel brass, albata, alpacca, is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver does not contain the eleme ...
remain the basic material for silver-plated cutlery. It is commonly used for mechanical and electrical equipment, medical equipment, zippers, jewelry items, and both for strings for instruments in the violin family, and for guitar frets.
Fender Musical Instruments The Fender Musical Instruments Corporation (FMIC, or simply Fender) is an American manufacturer of instruments and amplifiers. Fender produces acoustic guitars, bass amplifiers and public address equipment, however it is best known for its so ...
used "CuNiFe" magnets in their "Wide Range
Humbucker A humbucking pickup, humbucker, or double coil, is a type of guitar pickup that uses two wire coils to cancel out the noisy interference picked up by coil pickups. In addition to electric guitar pickups, humbucking coils are sometimes used in ...
" pickup for various
Telecaster The Fender Telecaster, colloquially known as the Tele , is an electric guitar produced by Fender. Together with its sister model the Esquire, it is the world's first mass-produced, commercially successfulLes Paul had built a prototype solid body ...
and Starcaster
guitars The guitar is a fretted musical instrument that typically has six strings. It is usually held flat against the player's body and played by strumming or plucking the strings with the dominant hand, while simultaneously pressing selected string ...
during the 1970s. For high-quality cylinder locks and locking systems, cylinder cores are made from wear-resistant cupronickel. Cupronickel has been used as an alternative to traditional steel brake lines, as it does not rust. Since cupronickel is much softer than steel, it bends and flares more easily, and the same property allows it to form a better seal with hydraulic components.


Properties

Cupronickel lacks a copper color due to nickel's high electronegativity, which causes a loss of one electron in copper's d-shell (leaving 9 electrons in the d-shell versus pure copper's typical 10 electrons). Important properties of cupronickel alloys include
corrosion resistance 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 engine ...
, inherent resistance to macrofouling, good tensile strength, excellent
ductility Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
when annealed,
thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
and expansion characteristics amenable for
heat exchangers A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
and condensers, good thermal conductivity and ductility at
cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
temperatures and beneficial antimicrobial touch surface properties. The alloys are: * These values may vary in other standards Subtle differences in
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 engine ...
resistance and strength determine which alloy is selected. Descending the table, the maximum allowable flow rate in piping increases, as does the tensile strength. In seawater, the alloys have excellent corrosion rates which remain low as long as the maximum design flow
velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...
is not exceeded. This velocity depends on geometry and pipe diameter. They have high resistance to
crevice corrosion Crevice corrosion refers to corrosion occurring in occluded spaces such as interstices in which a stagnant solution is trapped and not renewed. These spaces are generally called crevices. Examples of crevices are gaps and contact areas between pa ...
,
stress corrosion cracking Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. SCC ...
and
hydrogen embrittlement Hydrogen embrittlement (HE), also known as hydrogen-assisted cracking or hydrogen-induced cracking (HIC), is a reduction in the ductility of a metal due to absorbed hydrogen. Hydrogen atoms are small and can permeate solid metals. Once absorbe ...
that can be troublesome to other alloy systems. Copper-nickels naturally form a thin protective surface layer over the first several weeks of exposure to seawater and this provides its ongoing resistance. Additionally, they have a high inherent
biofouling Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or small animals where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers that ...
resistance to attachment by macrofoulers (e.g.
seagrasses Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...
and
molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...
) living in the seawater. To use this property to its full potential, the alloy needs to be free of the effects of, or insulated from, any form of
cathodic protection Cathodic protection (CP; ) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded " sacrifi ...
. However, Cu–Ni alloys can show high corrosion rates in polluted or stagnant seawater when
sulfides Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...
or
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
are present. It is important, therefore, to avoid exposure to such conditions, particularly during commissioning and refit while the surface films are maturing.
Ferrous sulfate Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula Fe SO4·''x''H2O. These compounds exist most commonly as the heptahydrate (''x'' = 7) but several values for x are know ...
dosing Dosing generally applies to feeding chemicals or medicines when used in small quantities. For medicines the term '' dose'' is generally used. In the case of inanimate objects the word dosing is typical. The term dose titration, referring to stepw ...
to sea water systems can provide improved resistance. As copper and nickel alloy with each other easily and have simple structures, the alloys are ductile and readily fabricated. Strength and hardness for each individual alloy is increased by
cold working In metallurgy, cold forming or cold working is any metalworking process in which metal is shaped below its recrystallization temperature, usually at the ambient temperature. Such processes are contrasted with hot working techniques like hot rol ...
; they are not hardened by
heat treatment Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are al ...
. Joining of 90–10 (C70600) and 70–30 (C71500) is possible by both
welding Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as bra ...
or
brazing Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from we ...
. They are both weldable by the majority of techniques, although autogenous (welding without weld consumables) or
oxyacetylene Principle of burn cutting Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the United States) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline or petrol, diesel, ...
methods are not recommended. The 70–30 rather than 90–10 weld consumables are normally preferred for both alloys and no after-welding heat treatment is required. They can also be welded directly to steel, providing a 65% nickel-copper weld consumable is used to avoid iron dilution effects. The C71640 alloy tends to be used as seamless tubing and expanded rather than welded into the tube plate. Brazing requires appropriate silver-base brazing alloys. However, great care must be taken to ensure that there are no stresses in the Cu–Ni being silver brazed, since any stress can cause intergranulary penetration of the brazing material, and severe stress cracking (see image). Thus, full annealing of any potential mechanical stress is necessary. Applications for Cu–Ni alloys have withstood the test of time, as they are still widely used and range from seawater system piping, condensers and
heat exchangers A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
in naval vessels, commercial shipping, multiple-stage flash desalination and power stations. They have also been used as splash zone cladding on offshore structures and protective cladding on boat hulls, as well as for solid hulls themselves.


Fabrication

Due to its
ductility Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
, cupronickel alloys can be readily fabricated in a wide variety of product forms and fittings. Cupronickel tubing can be readily expanded into tube sheets for the manufacturing of shell and tube
heat exchangers A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
. Details of fabrication procedures, including general handling, cutting and machining, forming, heat treatment, preparing for welding, weld preparations, tack welding, welding consumables, welding processes, paintina, mechanical properties of welds, and tube and pipe bending are available.


Standards

ASTM ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
, EN, and
ISO ISO is the most common abbreviation for the International Organization for Standardization. ISO or Iso may also refer to: Business and finance * Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007 * Is ...
standards exist for ordering wrought and cast forms of cupronickel.
Thermocouple A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the ...
s and
resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active ...
s whose resistance is stable across changes in temperature contain alloy
constantan Constantan is a proprietary name for a copper–nickel alloy also known as Eureka, Advance, and Ferry. It usually consists of 55% copper and 45% nickel. Its main feature is the low thermal variation of its resistivity, which is constant ...
, which consists of 55% copper and 45% nickel.


History


Chinese history

Cupronickel alloys were known as "white copper" to the
Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of v ...
since about the third century BC. Some weapons made during the
Warring States period The Warring States period () was an era in ancient Chinese history characterized by warfare, as well as bureaucratic and military reforms and consolidation. It followed the Spring and Autumn period and concluded with the Qin wars of conquest ...
were made with Cu-Ni alloys.Ancient Chinese weapons
an
A halberd of copper-nickel alloy, from the Warring States Period.
The theory of Chinese origins of
Bactria Bactria (; Bactrian: , ), or Bactriana, was an ancient region in Central Asia in Amu Darya's middle stream, stretching north of the Hindu Kush, west of the Pamirs and south of the Gissar range, covering the northern part of Afghanistan, southwe ...
n cupronickel was suggested in 1868 by Flight, who found that the coins considered the oldest cupronickel coins yet discovered were of a very similar alloy to Chinese ''paktong''.
Joseph Needham Noel Joseph Terence Montgomery Needham (; 9 December 1900 – 24 March 1995) was a British biochemist, historian of science and sinologist known for his scientific research and writing on the history of Chinese science and technology, ini ...
, Ling Wang, Gwei-Djen Lu,
Tsuen-hsuin Tsien Tsien Tsuen-hsuin (; 11 January 19109 April 2015), also known as T.H. Tsien, was a Chinese-American bibliographer, librarian, and sinologist who served as a professor of Chinese literature and library science at the University of Chicago, and wa ...
, Dieter Kuhn, Peter J Golas
''Science and civilisation in China''
Cambridge University Press: 1974, , pp. 237–250
The author-scholar, Ho Wei, precisely described the process of making cupronickel in about 1095 AD. The ''paktong'' alloy was described as being made by adding small pills of naturally occurring ''yunnan'' ore to a bath of molten copper. When a crust of
slag Slag is a by-product of smelting ( pyrometallurgical) ores and used metals. Broadly, it can be classified as ferrous (by-products of processing iron and steel), ferroalloy (by-product of ferroalloy production) or non-ferrous/base metals (by-pr ...
formed,
saltpeter Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and nitra ...
was added, the alloy was stirred and the
ingot An ingot is a piece of relatively pure material, usually metal, that is cast into a shape suitable for further processing. In steelmaking, it is the first step among semi-finished casting products. Ingots usually require a second procedure of sha ...
was immediately
cast Cast may refer to: Music * Cast (band), an English alternative rock band * Cast (Mexican band), a progressive Mexican rock band * The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis * ''Cast'', a 2012 album by Trespassers William ...
. Zinc is mentioned as an ingredient but there are no details about when it was added. The ore used is noted as solely available from
Yunnan Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the ...
, according to the story:
"San Mao Chun were at Tanyang during a famine year when many people died, so taking certain chemicals, Ying projected them onto silver, turning it into gold, and he also transmuted iron into silver – thus enabling the lives of many to be saved hrough purchasing grain through this fake silver and goldThereafter all those who prepared chemical powders by heating and transmuting copper by projection called their methods "Tanyang techniques".
The late Ming and Qing literature have very little information about ''paktong''. However, it is first mentioned specifically by name in the ''Thien Kung Khai Wu'' of ''circa'' 1637:
"When ''lu kan shih'' (zinc carbonate,
calamine Calamine, also known as calamine lotion, is a medication used to treat mild itchiness. This includes from sunburn, insect bites, poison ivy, poison oak, and other mild skin conditions. It may also help dry out skin irritation. It is applied ...
) or ''wo chhein'' (zinc metal) is mixed and combined with ''chih thung'' (copper), one gets 'yellow bronze' (ordinary brass). When ''phi shang'' and other arsenic substances are heated with it, one gets 'white bronze' or white copper: ''pai thong''. When
alum An alum () is a type of chemical compound, usually a hydrated double sulfate salt of aluminium with the general formula , where is a monovalent cation such as potassium or ammonium. By itself, "alum" often refers to potassium alum, with the ...
and
niter Niter or nitre is the mineral form of potassium nitrate, KNO3. It is a soft, white, highly soluble mineral found primarily in arid climates or cave deposits. Historically, the term ''niter'' was not well differentiated from natron, both of ...
and other chemicals are mixed together one gets ''ching thung'': green bronze."
Ko Hung stated in 300 AD: "The Tanyang copper was created by throwing a mercuric elixir into Tanyang copper and heated- gold will be formed." However, the ''Pha Phu Tsu'' and the ''Shen I Ching'' describing a statue in the Western provinces as being of silver, tin, lead and Tanyang copper – which looked like gold, and could be forged for plating and inlaying vessels and swords.
Joseph Needham Noel Joseph Terence Montgomery Needham (; 9 December 1900 – 24 March 1995) was a British biochemist, historian of science and sinologist known for his scientific research and writing on the history of Chinese science and technology, ini ...
''et al.'' argue that cupronickel was at least known as a unique alloy by the Chinese during the reign of Liu An in 120 BC in Yunnan. Moreover, the Yunnanese State of Tien was founded in 334 BC as a colony of the Chu. Most likely, modern ''paktong'' was unknown to Chinese of the day – but the naturally occurring Yunnan ore cupronickel alloy was likely a valuable internal trade commodity.


Greco-Bactrian coinage

In 1868, W. Flight discovered a
Greco-Bactrian The Bactrian Kingdom, known to historians as the Greco-Bactrian Kingdom or simply Greco-Bactria, was a Hellenistic-era Greek state, and along with the Indo-Greek Kingdom, the easternmost part of the Hellenistic world in Central Asia and the Ind ...
coin comprising 20% nickel that dated from 180 to 170 BCE with the bust of
Euthydemus II Euthydemus II (Greek: ) was a Greco-Bactrian king who ruled in Bactria in 185-180 BCE. Rule Son of Demetrius I of Bactria, Euthydemus II became king in the 180s BCE, either after his father's death or as a sub-king to him. The style and rare nick ...
on the obverse. Coins of a similar alloy with busts of his younger brothers,
Pantaleon Pantaleon, also known as Panteleimon, (Greek: ) was a Greek king who reigned some time between 190–180 BC in Bactria and India. He was a younger contemporary or successor of the Greco-Bactrian king Demetrius, and is sometimes believed to hav ...
and Agathocles, were minted around 170 BCE. The composition of the coins was later verified using the traditional wet method and X-ray fluorescence spectrometry. Cunningham in 1873 proposed the "Bactrian nickel theory," which suggested that the coins must have been the result of overland trade from China through India to Greece. Cunningham's theory was supported by scholars such as W. W. Tarn, Sir John Marshall, and J. Newton Friend, but was criticized by E. R. Caley and S. van R. Cammann. In 1973, Cheng and Schwitter in their new analyses suggested that the Bactrian alloys (copper, lead, iron, nickel and cobalt) were closely similar to the Chinese ''paktong'', and of nine known Asian nickel deposits, only those in China could provide the identical chemical compositions. Cammann criticized Cheng and Schwitter's paper, arguing that the decline of cupronickel currency should not have coincided with the opening of the Silk Road. If the Bactrian nickel theory were true, according to Cammann, the
Silk Road The Silk Road () was a network of Eurasian trade routes active from the second century BCE until the mid-15th century. Spanning over 6,400 kilometers (4,000 miles), it played a central role in facilitating economic, cultural, political, and rel ...
would have increased the supply of cupronickel. However, the end of Greco-Bactrian cupronickel currency could be attributed to other factors such as the end of the House of Euthydemus.


European history

The alloy seems to have been rediscovered by the West during
alchemy Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Greek: χυμεία, ''khumeía'') is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practiced in China, India, the Muslim worl ...
experiments. Notably,
Andreas Libavius Andreas Libavius or Andrew Libavius was born in Halle, Germany c. 1550 and died in July 1616. Libavius was a renaissance man who spent time as a professor at the University of Jena teaching history and poetry. After which he became a physician a ...
, in his ''Alchemia'' of 1597, mentions a surface-whitened copper ''aes album'' by mercury or silver. But in ''De Natura Metallorum'' in ''Singalarum'' Part 1, published in 1599, the same term was applied to "tin" from the East Indies (modern-day
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guinea. In ...
and the
Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...
) and given the Spanish name, ''tintinaso''. Richard Watson of Cambridge appears to be the first to discover that cupronickel was an alloy of three metals. In attempting to rediscover the secret of white-copper, Watson critiqued
Jean-Baptiste Du Halde Jean-Baptiste Du Halde (; 1 February 1674 – 18 August 1743) was a French Jesuit historian specializing in China. He did not travel to China, but collected seventeen Jesuit missionaries' reports and provided an encyclopedic survey of the his ...
's ''History of China'' (1688) as confusing the term ''paktong'., He noted the Chinese of his day did not form it as an alloy but rather
smelted Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and ...
readily available unprocessed ore:
"...appeared from a vast series of experiments made at Peking- that it occurred naturally as an ore mined at the region, the most extraordinary copper is ''pe-tong'' or white copper: it is white when dug out of the mine and even more white within than without. It appears, by a vast number of experiments made at Peking, that its colour is owing to no mixture; on the contrary, all mixtures diminish its beauty, for, when it is rightly managed it looks exactly like silver and were there not a necessity of mixing a little tutenag or such metal to soften it, it would be so much more the extraordinary as this sort of copper is found no where but in China and that only in the Province of Yunnan". Notwithstanding what is here said, of the colour of the copper being owing to no mixture, it is certain the Chinese white copper as brought to us, is a mixt ic: mixedmetal; so that the ore from which it was extracted must consist of various metallic substances; and from such ore that the natural ''
orichalcum Orichalcum or aurichalcum is a metal mentioned in several ancient writings, including the story of Atlantis in the ''Critias'' of Plato. Within the dialogue, Critias (460–403 BC) claims that orichalcum had been considered second only to go ...
'' if it ever existed, was made."
During the peak European importation of Chinese white-copper from 1750 to 1800, increased attention was made to its discovering its constituents. Peat and Cookson found that "the darkest proved to contain 7.7% nickel and the lightest said to be indistinguishable from silver with a characteristic bell-like resonance when struck and considerable resistance to corrosion, 11.1%". Another trial by Andrew Fyfe estimated the nickel content at 31.6%. Guesswork ended when James Dinwiddie of the Macartney Embassy brought back in 1793, at considerable personal risk (smuggling of ''paktong'' ore was a capital crime by the Chinese Emperor), some of the ore from which ''paktong'' was made.Mcneil I Staff, Ian McNeil ''Encyclopaedia of the History of Technology'': Routledge: 2002: : pp98 Cupronickel became widely understood, as published by E. Thomason, in 1823, in a submission, later rejected for not being new knowledge, to the
Royal Society of Arts The Royal Society for the Encouragement of Arts, Manufactures and Commerce (RSA), also known as the Royal Society of Arts, is a London-based organisation committed to finding practical solutions to social challenges. The RSA acronym is used m ...
. Efforts in Europe to exactly duplicate the Chinese ''paktong'' failed due to a general lack of requisite complex cobalt-nickel-arsenic naturally occurring ore. However, the Schneeberg district of Germany, where the famous '' Blaufarbenwerke'' made
cobalt blue Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminum(III) oxide (alumina) at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. Cobalt blue is lighte ...
and other pigments, solely held the requisite complex cobalt-nickel-arsenic ores in Europe. At the same time, the
Prussia Prussia, , Old Prussian: ''Prūsa'' or ''Prūsija'' was a German state on the southeast coast of the Baltic Sea. It formed the German Empire under Prussian rule when it united the German states in 1871. It was '' de facto'' dissolved by an ...
n ''Verein zur Beförderung des Gewerbefleißes'' (Society for the Improvement of Business Diligence/Industriousness) offered a prize for the mastery of the process. Unsurprisingly, Dr E.A. Geitner and J.R. von Gersdoff of Schneeberg won the prize and launched their "
German silver Nickel silver, Maillechort, German silver, Argentan, new silver, nickel brass, albata, alpacca, is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver does not contain the eleme ...
" brand under the trade names '' Argentan'' and ''Neusilber'' (new silver). In 1829, Percival Norton Johnston persuaded Dr. Geitner to establish a
foundry A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal into a mold, and removing the mold material after the metal has solidified as it cools. The most common metals pr ...
in Bow Common behind Regents' Park Canal in London, and obtained ingots of nickel-silver with the composition 18% Ni, 55% Cu and 27% Zn. Between 1829 and 1833, Percival Norton Johnson was the first person to refine cupronickel on the British Isles. He became a wealthy man, producing in excess of 16.5 tonnes per year. The alloy was mainly made into
cutlery Cutlery (also referred to as silverware, flatware, or tableware), includes any hand implement used in preparing, serving, and especially eating food in Western culture. A person who makes or sells cutlery is called a cutler. The city of Sheffie ...
by the
Birmingham Birmingham ( ) is a city and metropolitan borough in the metropolitan county of West Midlands in England. It is the second-largest city in the United Kingdom with a population of 1.145 million in the city proper, 2.92 million in the West ...
firm William Hutton and sold under the trade-name "Argentine". Johnsons' most serious competitors, Charles Askin and Brok Evans, under the brilliant chemist Dr. EW Benson, devised greatly improved methods of cobalt and nickel suspension and marketed their own brand of nickel-silver, called " British Plate". By the 1920s, a 70–30 copper-nickel grade was developed for naval condensers. Soon afterwards, a 2% manganese and 2% iron alloy now known as alloy C71640 was introduced for a UK power station which needed better erosion resistance because the levels of entrained sand in the seawater. A 90–10 alloy first became available in the 1950s, initially for seawater piping, and is now the more widely used alloy.


See also

*
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 ...
(copper alloyed with
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 ...
) *
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 such ...
(copper alloyed with
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 ...
) * Copper alloys in aquaculture *
Freeze branding Freeze branding (sometimes called CryoBranding and the resulting brands, trichoglyphs) is a technique involving a cryogenic coolant instead of heat to produce permanent marks on a variety of animals. The coolant is used to lower the temperature of ...


References

{{reflist


External links


Copper-Nickel Alloys


(Source: German Copper Institute (DKI))]
Copper-Nickel Alloys for Seawater Corrosion Resistance and Antifouling - A State of the Art Review
(C.A. Powell and H.T. Michels; Corrosion 2000, NACE March 2000 ( NACE)) Nickel alloys Copper alloys Coinage metals and alloys