Cupronickel
Overview
 
Cupronickel or copper-nickel or "cupernickel" is an alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 that contains nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 and strengthening elements, such as iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 and manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

. Cupronickel is highly resistant to corrosion in seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

, because its electrode potential
Electrode potential
Electrode potential, E, in electrochemistry, according to an IUPAC definition, is the electromotive force of a cell built of two electrodes:* on the left-hand side is the standard hydrogen electrode, and...

 is adjusted to be neutral with regard to seawater. Because of this, it is used for piping, heat exchangers and condensers in seawater systems as well as marine hardware, and sometimes for the propeller
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...

s, crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

s and hull
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

s of premium tugboat
Tugboat
A tugboat is a boat that maneuvers vessels by pushing or towing them. Tugs move vessels that either should not move themselves, such as ships in a crowded harbor or a narrow canal,or those that cannot move by themselves, such as barges, disabled ships, or oil platforms. Tugboats are powerful for...

s, fishing boats and other working boat
Boat
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

s.

A more familiar common use is in silver-coloured modern circulation coin
Coin
A coin is a piece of hard material that is standardized in weight, is produced in large quantities in order to facilitate trade, and primarily can be used as a legal tender token for commerce in the designated country, region, or territory....

s.
Encyclopedia
Cupronickel or copper-nickel or "cupernickel" is an alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 that contains nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 and strengthening elements, such as iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 and manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

. Cupronickel is highly resistant to corrosion in seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

, because its electrode potential
Electrode potential
Electrode potential, E, in electrochemistry, according to an IUPAC definition, is the electromotive force of a cell built of two electrodes:* on the left-hand side is the standard hydrogen electrode, and...

 is adjusted to be neutral with regard to seawater. Because of this, it is used for piping, heat exchangers and condensers in seawater systems as well as marine hardware, and sometimes for the propeller
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...

s, crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

s and hull
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

s of premium tugboat
Tugboat
A tugboat is a boat that maneuvers vessels by pushing or towing them. Tugs move vessels that either should not move themselves, such as ships in a crowded harbor or a narrow canal,or those that cannot move by themselves, such as barges, disabled ships, or oil platforms. Tugboats are powerful for...

s, fishing boats and other working boat
Boat
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

s.

A more familiar common use is in silver-coloured modern circulation coin
Coin
A coin is a piece of hard material that is standardized in weight, is produced in large quantities in order to facilitate trade, and primarily can be used as a legal tender token for commerce in the designated country, region, or territory....

s. A typical mix is 75% copper, 25% nickel, and a trace amount of manganese. In the past true silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 coins were debased
Debasement
Debasement is the practice of lowering the value of currency. It is particularly used in connection with commodity money such as gold or silver coins...

 with cupronickel. Despite high copper content, the colour of cupro-nickel remarkably is silver.

It is used in thermocouple
Thermocouple
A thermocouple is a device consisting of two different conductors that produce a voltage proportional to a temperature difference between either end of the pair of conductors. Thermocouples are a widely used type of temperature sensor for measurement and control and can also be used to convert a...

s, and resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...

s whose resistance is stable across changes in temperature contain the 55% copper-45% nickel alloy constantan
Constantan
Constantan is a copper-nickel alloy usually consisting of 55% copper and 45% nickel.Also known as Eureka.Its main feature is its resistivity which is constant over a wide range of temperatures...

.

Monel
Monel
Monel is a trademark of Special Metals Corporation for a series of nickel alloys, primarily composed of nickel and copper, with some iron and other trace elements. Monel was created by David H. Browne, chief metallurgist for International Nickel Co...

 metal is a nickel-copper alloy, containing minimum 63% nickel.

Other names

Aside from cupro-nickel, many other terms exist which describe the same material. Still registered as tradenames are Alpaka or Alpacca (registered trademark), Argentan Minargent, the French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

 term name Cuivre blanc Occasionally cupro-nickel is also referred to as "hotel silver", plata alemana (Spanish
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...

 for "German Silver"), "German silver" and "Chinese silver".

History

Cupro-nickel was known to the Romans as an artificial "white" gold or silver termed "claudianum" and very possibly the"molybdochalcum
Molybdochalkos
Molybdochalkos is an alloy of copper and lead. It was known by Greek alchemists as early as the 10th century.-External links:*...

" of the Alexandrians.

The cupro-nickel alloy was known by Chinese
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 since circa 3rd century BCE as "white copper" (some weapons from the Warring States Period
Warring States Period
The Warring States Period , also known as the Era of Warring States, or the Warring Kingdoms period, covers the Iron Age period from about 475 BC to the reunification of China under the Qin Dynasty in 221 BC...

 were in Cu-Ni alloy).

The ancient Greeks were producing it and a lower quality imitation of it in the Aegean Bronze Age and known as "orichalcum". The Greco-Bactrian
Greco-Bactrian Kingdom
The Greco-Bactrian Kingdom was the easternmost part of the Hellenistic world, covering Bactria and Sogdiana in Central Asia from 250 to 125 BC...

 kings issued the first cupro-nickel coins, with Euthydemus II
Euthydemus II
Euthydemus II was a son of Demetrius I of Bactria, and became king of Bactria in the 180s BCE, either after his father's death or as a sub-king to him. The style and rare nickel alloys of his coins associates him closely in time with the king Agathocles but their precise relation remains uncertain...

, dating from 180 to 170 BCE, and his younger brothers Pantaleon
Pantaleon
Pantaleon was a Greek king who reigned some time between 190–180 BCE in Bactria and India. He was a younger contemporary or successor of the Greco-Bactrian king Demetrius, and is sometimes believed to have been his brother and/or subking...

 and Agathocles
Agathocles of Bactria
Agathocles Dikaios was a Buddhist Indo-Greek king, who reigned between around 190 and 180 BCE. He might have been a son of Demetrius and one of his sub-kings in charge of the Paropamisade between Bactria and India...

 around 170 BCE.

The theory of Chinese origins of Bactrian cupro-nickel was suggested in 1868 by Flight, who found the coins and considered the oldest cupro-nickel coins yet discovered were of a very similar alloy to Chinese paktong. Cunningham in 1873 argued the coins must have been the result of overland trade from China, through India to Greece — highly controversial at the time and much derided. In 1973, Cheng and Schwitter in their new analyses argued the Bactrian alloys (copper, lead, iron, nickel and cobalt) were closely similar to Chinese paktong, and that out of nine known Asian nickel deposits, only those in China could provide same identical chemical content ratios. However this hypothesis, although widely publicised, was later disproven by a perhaps over-enthusiastic oversight of the well-known Persian arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

-nickel mines much closer to Bactria and known to be exploited by the Greeks and Persians.

Chinese history of cupronickel

The author-scholar Ho Wei describes most exactly the process in circa 1095 CE, which suggest the Chinese were not aware that nickel was a metal in its own right. The paktong alloy was described as being made from adding small pills of naturally-occurring "Yunnan" ore to a bath of molten copper. When a crust of slag
Slag
Slag is a partially vitreous by-product of smelting ore to separate the metal fraction from the unwanted fraction. It can usually be considered to be a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and metal atoms in the elemental form...

 formed, saltpeter
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

 was added, the alloy stirred and the ingot
Ingot
An ingot is a material, usually metal, that is cast into a shape suitable for further processing. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods.-Uses:...

 immediately cast
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...

. Zinc is mentioned as an ingredient — but not detailed when exactly it was added. The ore used is noted as solely available from Yunnan, related from 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 [through purchasing grain through this fake silver and gold]
Thereafter all those who prepared chemical powders by heating and transmuting copper by projection called their methods "Tanyang techniques".


The late Ming and Ching 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
Calamine is a mixture of zinc oxide with about 0.5% ferric oxide . It is the main ingredient in calamine lotion and is used as an antipruritic to treat mild pruritic conditions such as sunburn, eczema, rashes, poison ivy, chickenpox, and insect bites and stings...

) 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
Alum
Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate with the formula KAl2.12H2O. The wider class of compounds known as alums have the related empirical formula, AB2.12H2O.-Chemical properties:Alums are...

 and niter
Niter
Niter or nitre is the mineral form of potassium nitrate, KNO3, also known as saltpeter or saltpetre . Historically, the term "niter" – cognate with "natrium", a Latin word for sodium – has been very vaguely defined, and it has been applied to a variety of other minerals and chemical compounds,...

 and other chemicals are mixed together one gets ching thung: green bronze.


Ko Hung of the 300 CE stated:" 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.

Needham et al. argue that cupro-nickel was at least known as a unique alloy by the Chinese during the reign of Liu An in 120 BCE in Yunnan. Moreover the Yunnanese State of Tien was founded in 334 BCE as a colony of the Chu. Most likely modern paktong was unknown to Chinese of the day — but the naturally occurring Yunnan ore cupro-nickel alloy was likely a valuable internal trade commodity.

Western re-discovery

The alloy seems to have been re-discovered by the West during alchemy
Alchemy
Alchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...

 experiments. Notably Andreas Libavius
Andreas Libavius
Andreas Libavius was a German doctor and chemist.-Life:Libavius was born in Halle, Germany, as Andreas Libau. In Halle he attended the gymnasium and studied from the year 1576 in University of Wittenberg. From 1577 on he studied in the University of Jena in the faculties of philosophy and history...

, 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, of 1599 the same term was applied to '"tin" from the East Indies (modern-day Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

 and the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

) and given the Spanish name: tintinaso.

Richard Watson of Cambridge appears to be the first to discover cupro-nickel was an alloy of three metals. In attempting to re-discover the secret of white-copper, Watson critiqued Jean-Baptiste Du Halde
Jean-Baptiste Du Halde
Jean-Baptiste Du Halde was a French Jesuit historian specializing in China. Although he had not gone to China, he collected seventeen Jesuit missionaries' reports and provided encyclopedic survey on Chinese history, culture and society....

'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 smelted
Smelting
Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores...

 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 [sic: mixed] metal; so that the ore from which it was extracted must consist of various metallic substances; and from such ore that the natural orichalcum if it ever existed, was made".


During the peak European importation of Chinese white-copper during 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
Andrew Fyfe (chemist)
-Life:He was born 18 January 1792, the son of Andrew Fyfe the Elder. He graduated M.D. at the University of Edinburgh in 1814, and became fellow of the Edinburgh College of Surgeons in 1818, and president in 1842-3....

 estimated the nickel content at 31.6%. Guesswork ended when James Dinwiddie of the Macartney Embassy of 1793 brought back, 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. Cupro-nickel 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
Royal Society of Arts
The Royal Society for the encouragement of Arts, Manufacturers and Commerce is a British multi-disciplinary institution, based in London. The name Royal Society of Arts is frequently used for brevity...

.

Efforts to duplicate exactly the Chinese paktong failed in Europe due to a general lack of requisite complex cobalt-nickel-arsenic naturally occurring ore. However, the Schneeburg
Schneeburg
Schneeburg is a castle ruin between Ebringen and Freiburg, Germany. The ruins are at an altitude of 516 metres on the western summit of Schönberg.-History:...

 district of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, where the famous Blaufarbenwerke made cobalt blue
Cobalt blue
Cobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses...

 and other pigments, solely held the requisite complex cobalt-nickel-arsenic ores in Europe.

At the same time the Prussian Verein zur Beförderung des Gewerbefleißes ("Society for the Improvement of Business Diligence/Industriousness") offered a prize for the mastery of the process and unsurprisingly, Dr E.A. Geitner and J.R. von Gersdoff of Schneeburg duly won the prize and launched their German silver under the trade name Argentan and Neusilber ("new Silver")

In 1829, Percival Norton Johnston persuaded Dr Geitner to establish a foundry
Foundry
A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal in a mold, and removing the mold material or casting after the metal has solidified as it cools. The most common metals processed are aluminum and cast iron...

 in Bow Common behind Regents' Park Canal in London and obtained ingots of nickel-silver of 18% Ni, 55% Cu and 27% Zn.
Between 1829 and 1833—Percival Norton Johnson was the first man to refine cupro-nickel on the British Isles: and became a wealthy man producing in excess of 16.5 tonnes per year, mainly made into cutlery
Cutlery
Cutlery refers to any hand implement used in preparing, serving, and especially eating food in the Western world. It is more usually known as silverware or flatware in the United States, where cutlery can have the more specific meaning of knives and other cutting instruments. This is probably the...

 by the Birmingham
Birmingham
Birmingham is a city and metropolitan borough in the West Midlands of England. It is the most populous British city outside the capital London, with a population of 1,036,900 , and lies at the heart of the West Midlands conurbation, the second most populous urban area in the United Kingdom with a...

 firm William Hutton and sold under the trade-name "Argentine".
Johnsons' most serious competitor, 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: British Plate.

Coinage

In Europe, Switzerland pioneered the nickel billion coinage in 1850, with the addition of silver. In 1879, Switzerland adopted the far cheaper 75:25 copper to nickel ratio then being used by the Belgians
Belgians
Belgians are people originating from the Kingdom of Belgium, a federal state in Western Europe.-Etymology:Belgians are a relatively "new" people...

, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, and Germany.

In part due to silver hoarding in the Civil War, the United States Mint first used cupro-nickel for circulating coinage in three cent
Three-cent piece (United States coin)
The United States three cent piece was a unit of currency equaling 3/100th of a United States dollar. The mint produced two different three-cent coins: the three-cent silver and the three-cent nickel. Its purchasing power in 1851 would be equivalent to $ today.-History:The three cent coin has an...

 pieces starting in 1865 and then for five cent
Nickel (United States coin)
The nickel is a five-cent coin, representing a unit of currency equaling five hundredths of one United States dollar. A later-produced Canadian nickel five-cent coin was also called by the same name....

 pieces starting in 1866. Prior to these dates, both denominations had been made only in silver in the United States.
Cupro-nickel is the cladding
Cladding (metalworking)
Cladding is the bonding together of dissimilar metals. It is distinct from welding or gluing as a method to fasten the metals together. Cladding is often achieved by extruding two metals through a die as well as pressing or rolling sheets together under high pressure.The United States Mint uses...

 on either side of United States Half Dollars
Kennedy half dollar
Within hours of the assassination of John F. Kennedy on November 22, 1963, Mint Director Eva Adams called Chief Engraver Gilroy Roberts, informing him that serious consideration was being given to depicting Kennedy on one of the larger silver coins: either the silver dollar, half dollar, or...

 (50¢) since 1971, and all quarters
Quarter (United States coin)
A quarter dollar, commonly shortened to quarter, is a coin worth ¼ of a United States dollar, or 25 cents. The quarter has been produced since 1796. The choice of 25¢ as a denomination, as opposed to 20¢ which is more common in other parts of the world, originated with the practice of dividing...

 (25¢) and dimes
Dime (United States coin)
The dime is a coin 10 cents, one tenth of a United States dollar, labeled formally as "one dime". The denomination was first authorized by the Coinage Act of 1792. The dime is the smallest in diameter and is the thinnest of all U.S...

 (10¢) made after 1964. Currently some circulating coins like the United States Jefferson Nickel
Nickel (United States coin)
The nickel is a five-cent coin, representing a unit of currency equaling five hundredths of one United States dollar. A later-produced Canadian nickel five-cent coin was also called by the same name....

 (5¢), the Swiss franc
Swiss franc
The franc is the currency and legal tender of Switzerland and Liechtenstein; it is also legal tender in the Italian exclave Campione d'Italia. Although not formally legal tender in the German exclave Büsingen , it is in wide daily use there...

, and the South Korea
South Korea
The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...

n 500 and 100 won
South Korean won
The won is the currency of South Korea. A single won is divided into 100 jeon, the monetary subunit. The jeon is no longer used for everyday transactions, and appears only in foreign exchange rates...

 are made of solid cupro-nickel (75/25 ratio).

Marine engineering grades

By the 1920s, a 70–30 copper-nickel grade was developed for naval condensers. Soon afterwards, a 2% manganese and 2% iron alloy 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.

The alloys are:
UNS standard compositions* of wrought alloys (in at%). Maximum or range.
Alloy UNS No. Common name European spec Ni Fe Mn Cu
C70600 90-10 CuNi10Fe 9-11 1-1.8 1 Remainder
C71500 70-30 CuNi30Fe 29–33 0.4–1.0 1 Remainder
C71640 66-30-2-2 29–32 1.7–2.3 1.5–2.5 Remainder
  • These values may vary in other standards


There are subtle differences in corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...

 resistance and strength which determine which alloy is selected. Descending the table, the maximum allowable flow rate in piping increases as does the tensile strength.
Properties of some Cu-Ni alloys
Alloy Density
g/cm3
Thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....


W/(m·K)
TEC
Thermal expansion
Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...


µm/(m·K)
Electrical resisitivity
µOhm·cm
Elastic modulus
Elastic modulus
An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance's tendency to be deformed elastically when a force is applied to it...


GPa
Yield strength
MPa
Tensile strength
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...


MPa
90-10 8.9 50 17 19 135 105 275
70-30 8.95 29 16 34 152 125 360
66-30-2-2 8.86 25 15.5 50 156 170 435


In seawater, the alloys have excellent corrosion rates which remain low as long as the maximum design flow velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...

 is not exceeded. This velocity depends on geometry and pipe diameter. They have high resistance to crevice corrosion
Crevice corrosion
Crevice corrosion refers to corrosion occurring in confined spaces to which the access of the working fluid from the environment is limited. These spaces are generally called crevices...

, stress corrosion cracking
Stress corrosion cracking
Stress corrosion cracking is the unexpected sudden failure of normally ductile metals subjected to a tensile stress in a corrosive environment, especially at elevated temperature in the case of metals. SCC is highly chemically specific in that certain alloys are likely to undergo SCC only when...

 and hydrogen embrittlement
Hydrogen embrittlement
Hydrogen embrittlement is the process by which various metals, most importantly high-strength steel, become brittle and fracture following exposure to hydrogen...

 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 on-going resistance. Additionally, they have a high inherent biofouling
Biofouling
Biofouling or biological fouling is the undesirable accumulation of microorganisms, plants, algae, or animals on wetted structures.-Impact:...

 resistance to attachment by macrofoulers (e.g. seagrasses and molluscs) living in the seawater. To use this property to its full potential, the alloy needs to be free of the effects or insulated from any form of cathodic protection
Cathodic protection
Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. The simplest method to apply CP is by connecting the metal to be protected with another more easily corroded "sacrificial metal" to act as the anode of the...

.

However, Cu-Ni alloys can show high corrosion rates in polluted or stagnant seawater when sulfides or ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 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 dosing
Dosing
Dosing generally applies to feeding chemicals or medicines in small quantities into a process fluid or to a living being at intervals or to atmosphere at intervals to give sufficient time for the chemical or medicine to react or show the results....

 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; they are not hardened by heat treatment
Heat treatment
Heat treating is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass...

. Joining of 90–10 (C70600) and 70-30 (C71500) is possible by both welding
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...

 or brazing
Brazing
Brazing is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux...

. They are both weldable by the majority of techniques although autogenous (welding without weld consumables) or oxy-acetylene methods are not recommended. 70-30 rather than 90-10 weld consumables are normally preferred for both alloys and no post-weld 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. Brazing requires appropriate silver-base brazing alloys. The C71640 alloy tends to be used as seamless tubing and expanded rather than welded into the tube plate.
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 in naval vessels, commercial shipping, multi-stage flash desalination and power stations. They have also been used as splash zone cladding on offshore structures
Offshore construction
Offshore construction is the installation of structures and facilities in a marine environment, usually for the production and transmission of electricity, oil, gas and other resources....

 and protective cladding on boat hulls as well as for solid hulls themselves.

Other usage

Single-core thermocouple cables use a single conductor pair of thermocouple conductors such as iron-constantan, copper constantan or nickel-chromium/nickel-aluminium. These have the heating element of constantan or nickel-chromium alloy within a sheath of copper, cupro-nickel or stainless steel.

Beginning around the turn of the 20th century, bullet
Bullet
A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...

 jackets were commonly made from this material. It was soon replaced with gilding metal
Gilding metal
Gilding metal is a copper alloy, comprising 95% copper and 5% zinc. Technically, it is a brass.Gilding metal is used for various purposes, including the jackets of bullets, driving bands on some artillery shells, as well as enameled badges and other jewellery....

 to reduce metal fouling in the bore.

Currently, cupronickel remains the basic material for silver-plated cutlery. It is commonly used for mechanical and electrical equipment, medical equipment, zippers, jewelry items, and as material for strings for string instruments.

For high-quality cylinder lock and locking systems, the cylinder core is made from wear-resistant cupronickel.

See also

  • bronze
    Bronze
    Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...

     (copper alloyed with tin
    Tin
    Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

    )
  • brass
    Brass
    Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

     (copper alloyed with zinc
    Zinc
    Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

    )
  • nickel silver
    Nickel silver
    Nickel silver, also known as German silver, Argentann, new silver, nickel brass, albata,, or alpacca, is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver is named for its silvery appearance, but it contains no elemental silver...

     (another group of Cu-Ni alloys).
  • Copper alloys in aquaculture
    Copper alloys in aquaculture
    Recently, copper alloys have become important netting materials in aquaculture . Various other materials including nylon, polyester, polypropylene, polyethylene, plastic-coated welded wire, rubber, patented twine products , and galvanized steel are also used for netting in aquaculture fish...


External links

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