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Copper wire cable. Image Credit: Shutterstock.com/Flegere

Copper: Definition, Composition, Types, Properties, and Applications

Learn more about this material in full detail and how it can be used in manufacturing.

Xomety X
By Team Xometry
April 6, 2023
 15 min read
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Copper is a chemical element that is also a metal. Its key properties are that it has excellent electrical conductivity, high thermal conductivity, and good corrosion resistance. It is also ductile and has an interesting reddish-brown color. The combination of these properties leads to the wide application of copper for engineering and aesthetic uses.

What Is Copper?

Copper is a chemical element, number 29 on the periodic table of elements. The copper element symbol is Cu, from the Latin “cuprum”. It is a ductile metal with a reddish-brown color. It is applied widely due to its high thermal and electrical conductivity.

What Is the History of Copper?

The history of copper dates back to 8,700 BC. A copper pendant that was discovered in Northern Iraq has been dated back to approximately that date and is currently thought to be the oldest object made of copper. Copper has been a crucial metal in many ancient civilizations, but it is generally agreed that the Mesopotamians (in Northern Iraq) discovered copper. In fact, a period in prehistory is the copper age between 5,500 BC and 4,000 BC, usually called the Chalcolithic Age from the Greek words for copper (chalkos) and rock (lithos).

Copper is one of few metals that can occur naturally in its native metallic form. This is different from most metals that need to be extracted via metallurgy from an ore. In places where native copper occurs, the technology of metallurgy was not necessary for those civilizations to begin to work with copper to form weapons and ornaments.

What Is the Other Term for Copper?

The other term for copper is the Latin word cuprum, which gives copper its symbol Cu on the periodic table of elements. The Latin name for copper was originally from the island of Cyprus, as the island was the major source of copper in ancient times. Cuprum was the “metal of Cyprus.”

What Is Copper Made Of?

Copper is a chemical element. It is made of only a single type of atom—it cannot be broken down into simpler substances. The copper atom has an atomic number of 29, which means that its atomic nucleus contains 29 protons.

Copper is extracted from natural ores—either a copper sulfide ore (such as chalcopyrite) or a copper oxide ore. These ores are mined, crushed, and processed to make copper. These copper ores are found in parts of North and South America (countries such as Chile and Peru), as well as in areas such as the Ural Mountains in Russia, and in Zambia and the Democratic Republic of Congo in Africa.

What Are the Different Processes To Make Copper?

The different processes to make copper are described below:

1. Mining

Mining of copper ores is usually done in large open pit mines. These are open, stepped holes in the ground that are gradually dug deeper. Explosives are used to blast the rock, and the resulting boulders are transported for crushing into smaller pieces for processing.

2. Extraction

According to the two common types of copper ore, there are two main purification processes. A hydrometallurgical process is used for oxide ores. The crushed ore is heaped and an acid-leaching solution is percolated through the heap. This creates a pregnant leach solution. A pyrometallurgical process is used for sulfide ores. The extraction of the ore is done by froth flotation and thickening according to the density of the particles.

3. Purification

For oxide ores, hydrometallurgy is used. This means that the pregnant leach solution is sent to a solvent extraction process to concentrate the copper in the solution. This solution is then sent to electrowinning, where electricity is used to deposit the solid copper. For sulfide ores, pyrometallurgy is used, which means that a smelter is used to create the raw copper. This is then purified further by electrorefining.

4. Alloying

Copper alloys are manufactured by first melting the alloying material, and then melting the copper to add to it. The molten mixture is then cast and allowed to cool and solidify.

5. Electrorefining

Electrorefining of copper involves electrolytically dissolving impure copper material into solution. Pure copper is electrochemically deposited on an electrode by applying an electrical current through the solution. This removes impurities from the copper to achieve higher purity. However, the process is expensive and has a very high electrical demand.

What Are the Characteristics of Copper?

Copper metal has the primary characteristics of being an excellent electrical and thermal conductor. It is also malleable and ductile, which means it can be bent relatively easily. This makes it easy to work with, for example, with cabling being flexible. Another key characteristic of copper metal is its corrosion resistance, particularly in water and seawater environments. Finally, copper has the advantage of being aesthetically appealing, as it has a reddish-brown color and can be polished.

What Is the Color of Copper?

Copper is typically a reddish-brown color. However, pure copper before oxidation is actually a pink color, but the formation of brown copper oxide happens so rapidly that any readily available copper will be the common reddish-brown. Copper can also have a green tarnish (such as on the Statue of Liberty)—this is a copper carbonate.

What Does Copper Look Like?

Copper looks like a reddish-brown shiny metal. Copper can be processed into many different practical forms, such as the wires shown in Figure 1 below, as well as plumbing pipes and electronics:

Slide 1 of 1
reels of copper wire
reels of copper wire
reels of copper wire

Copper wire reels.

Image Credit: Shutterstock.com/Parilov

What Are the Different Types of Copper?

Copper is available in different types for different applications. The properties and applications of each grade of copper depends on the purity of the copper and what alloying elements (if any) are included. Listed below are the different types of copper:

1. Copper Wire

Copper wire takes advantage of the metal’s excellent electrical conductivity. It is the most common conductor for most electrical applications. It is used for large currents in industry, and also for domestic use, right down to the wiring within your home for outlets and lights.

2. Copper Tubing

Copper tubing has been widely used for domestic drinking water systems due to its corrosion resistance and therefore its longevity. Over the past few decades, it has been the standard in most of the world to use copper tubing for household plumbing. The tubes are available in different diameters and gauges (wall thicknesses). The high cost of copper and the emergence of improved plastic tubing materials means copper is becoming less frequently selected.

3. Copper Alloys

The two most common copper alloys are brass (alloyed with zinc) and bronze (alloyed with tin). Brass is typically applied more widely. It is used for plumbing fixtures, musical instruments, and decorative items. The addition of zinc gives the alloy a higher strength and ductility. Bronze has very similar characteristics to copper, such as: its high thermal conductivity, excellent ductility, and resistance to saltwater corrosion. Bronze is therefore used for bearings and bushings, as well as ship impellers.

4. Pure Coppers

Pure copper is specifically prepared to ensure a minimum of impurities, maximizing the thermal and electrical properties of copper. Pure copper tends to be softer and less tough than copper with additives or minor alloying materials. It is ideally used in precision electrical components, for which its electrical conductivity and low thermal expansion are ideal.

5. Copper Nanoparticles

Copper nanoparticles are very small particles of copper, or copper-based materials, that are within the size range of 1–100 nm. Nanoparticles have been found to have behaviors different from those of bulk materials. In the case of copper nanoparticles, they show very high catalytic activity for industrial chemical reactions, likely due to their large surface-area-to-volume ratio. Further, copper nanoparticles have shown excellent antimicrobial effects.

6. Free-Machining Coppers

Free-machining coppers have minor amounts (<1%) of other alloying elements added to improve the machinability of the copper. Free-machining copper can then be more easily machined into items such as welding nozzles and soldering iron tips.

7. Copper Sheets and Plates

Copper sheets are thin sheets of copper (about 2 mm or less), while plates are thicker (up to 12 mm thick). Generally, these are available in different copper grades. The sheets are highly malleable and can be formed into different components.

8. Oxygen-Free Coppers

Oxygen-free coppers are melted under a granulated graphite bath to exclude oxygen. They are the purest coppers available, with minimal impurities due to the non-oxidizing conditions. Its high electrical conductivity and low volatile impurities make it suitable for use in high-vacuum electronics.

9. Electrolytic Coppers

Electrolytic coppers are refined by electrolysis within a solution to remove impurities. This high-purity grade of copper has high electrical conductivity and therefore is employed in various electrical components such as bus bars and windings.

What Are the Properties of Copper?

The properties of different types of copper are shown in Table 1:

Table 1: Copper Properties
Copper TypeCompositionPropertiesCommon UsesExamples
Copper Type
Copper Tubing
Composition
99.9% copper, < 0.04% phosphorus
Properties
Corrosion resistant, ductile
Common Uses
Water supply
Examples
Household plumbing piping
Copper Type
Brass
Composition
> 60% copper, ≤ 39% zinc
Properties
Higher strength and ductility
Common Uses
Plumbing, musical instruments
Examples
Faucets, trumpets
Copper Type
Bronze
Composition
88% copper, 12% tin
Properties
Excellent ductility and corrosion resistance
Common Uses
Static lubrication, seawater corrosion resistance
Examples
Bushes and bearings, ship propellers
Copper Type
Copper Nanoparticles
Composition
Varied
Properties
High catalytic activity, better antimicrobial activity
Common Uses
Dentistry, agriculture
Examples
Dental implants, pesticides
Copper Type
Free-Machining Copper
Composition
99% copper, < 0.5% sulfur, telluride
Properties
Higher machinability
Common Uses
Machined components
Examples
Welding nozzles, soldering iron tips
Copper Type
Oxygen-Free Copper
Composition
99.99% copper
Properties
Very good electrical conductivity
Common Uses
Specialist electronics
Examples
High-vacuum electronic components
Copper Type
Electrolytic Copper
Composition
99.9% copper
Properties
Very good electrical conductivity
Common Uses
Critical electrical components
Examples
Ground wires, bus bars

The properties of each grade are similar, but their differences result in a variety of applications.

What Are the Physical Properties of Copper?

The physical properties of the different types of copper are shown in Table 2 below:

Table 2: Copper Physical Properties
Copper TypeDensity (g/cm3)Melting Point (°C)Boiling Point (°C)DuctilityThermal Conductivity (W/m.K)
Copper Type
High purity copper (>99%)
Density (g/cm3)
8.9
Melting Point (°C)
1,083
Boiling Point (°C)
2,595
Ductility
0.5
Thermal Conductivity (W/m.K)
401
Copper Type
Free-machining copper
Density (g/cm3)
8.94
Melting Point (°C)
1,080
Boiling Point (°C)
n/a
Ductility
n/a
Thermal Conductivity (W/m.K)
377
Copper Type
Brass
Density (g/cm3)
8.73
Melting Point (°C)
930
Boiling Point (°C)
1,100
Ductility
n/a
Thermal Conductivity (W/m.K)
144
Copper Type
Bronze
Density (g/cm3)
8.8
Melting Point (°C)
910
Boiling Point (°C)
2,300
Ductility
n/a
Thermal Conductivity (W/m.K)
189

Table Credit: https://www.lenntech.com/

The physical properties depend on the percentage of copper in the material as well as the alloying elements

What Are the Chemical Properties of Copper?

The chemical properties of copper depend primarily on its oxidation state. The two oxidation states that commonly exist are Cu+ and Cu2+. Table 3 below gives some of the chemical properties of common compounds and conditions for copper: 

Table 3: Chemical Properties of Copper
Copper TypeReactivityOxidation Potential (V)Reduction Potential (V)Solubility (KSP)Corrosion Resistance
Copper Type
Cu+
Reactivity
Unreactive (Hydrogen > Copper > Silver)
Oxidation Potential (V)
-1
Reduction Potential (V)
1
Solubility (KSP)
Insoluble (oxide)
Corrosion Resistance
0.025 mm/y (seawater)
Copper Type
Cu2+
Reactivity
Unreactive (Hydrogen > Copper > Silver)
Oxidation Potential (V)
0
Reduction Potential (V)
0.34
Solubility (KSP)
2.2x10-2 (hydroxide)
Corrosion Resistance
0.025 mm/y (seawater)

These properties may vary for each specific copper compound (such as oxalates, sulfites, and sulfates.

What Are the Applications of Copper?

The applications of copper are found throughout everyday society. Listed below are some common examples:

1. Electronics

Copper is used widely in electronics as it has excellent electrical conductivity. It allows currents to be carried on smaller cross-sections of copper compared to aluminum, allowing less bulk to be used, and components to be smaller.

2. Architecture

Copper is used in architecture for an aesthetically striking appearance. It has been used for roofing and wall cladding, as well as gutters and rainwater downspouts.

3. Plumbing

Copper tubing is used widely for domestic water piping in households, due to its very good corrosion resistance.

4. Transportation

Copper is used extensively in modern vehicles due to the amount of electrical cabling used for complex electronics. As electric vehicles grow in market share, increasing amounts of copper are used for elements such as electric motors. This is due to copper’s excellent electrical conductivity, second only to silver.

5. Renewable Energy

Copper is used within the renewable energy market in a number of ways. For instance, wind turbines use copper within the generating turbines. Solar photovoltaic panels also require copper for connections and cabling.

6. Medical Equipment

Copper is used as a coating on medical equipment due to its antibacterial properties. In this way, it reduces the risk of infection in patients.

7. Electrical Wiring

Copper is used widely for electrical wiring due to its excellent electrical conductivity. The cross-section of copper required to carry a particular current effectively is less than other reasonably available materials such as aluminum.

8. Coinage

Copper has historically been used in coins for a number of reasons: it is malleable and therefore easily stamped, but still durable enough to survive in circulation. It also has antimicrobial properties and corrosion resistance.

9. Industrial Machinery

Copper is used in a variety of ways in industrial equipment, with services such as copper die casting. Apart from electrical applications such as motors and cabling, it is also used in heat exchangers such as refrigeration condensers. It may also be applied for particular chemical resistance.

What Are the Benefits of Copper?

Copper has a number of clear benefits which are listed below:

  1. Has excellent electrical conductivity, second only to silver, making it the most widely used conductor for electrical and electronic components globally.
  2. Has very good thermal conductivity, and therefore is used in heat exchangers, such as condensers in refrigeration and air conditioning units.
  3. Is corrosion-resistant, particularly in water and seawater applications, which has led to its widespread usage in plumbing piping for water systems.
  4. Is ductile and can be bent relatively easily. It is easy to work with in plumbing systems as well as in cabling.
  5. Is antimicrobial, which can be very useful in water conveyance, as well as in medical applications to protect the health of patients.

What Are the Health Benefits of Copper?

Copper is a trace mineral that is essential for human health in very small quantities. Copper plays a part in the body by promoting the absorption of iron, participating in the production of red blood cells, as well as the production of collagen. It is understood to improve the function of the immune system.

More research is needed, but there are some indications that copper can improve osteoporosis (low bone density), and there are unproven theories that copper bracelets can be used to relieve pain in the joints from arthritis.

Food groups that contain copper include leafy greens, whole grains, nuts, and seeds. Specific food items that are high in copper are oysters, shiitake mushrooms, sweet potatoes, and dark chocolate.

What Are the Limitations of Copper?

Copper has a number of limitations, some of which are listed below:

  1. Is relatively expensive compared to potential alternative materials such as: aluminum (electrical cabling) or plastics (water piping).
  2. Is relatively heavy compared to materials such as aluminum, so for overhead wires, it may not be practical.
  3. Oxidizes, particularly at high temperatures, and so has a limited life span if exposed to air.
  4. Presents a shock risk compared to the alternative signal transmission technology of fiber optics.
  5. Is toxic in large amounts, so it cannot be applied where regular ingestion of copper could occur, such as in utensils.

Does Copper Rust Easily?

Copper does not technically rust, as rust is an iron oxide and there is no iron in copper. However, copper does experience some limited surface corrosion. Copper is generally considered corrosion-resistant. It naturally has a reddish-brown color, which is due to the formation of a copper oxide passivation film on the metal’s surface. Over time, a green copper carbonate forms on the surface as the copper oxide reacts with water and carbon dioxide in the air.

Is Copper Poisonous to Humans?

Yes, copper can be poisonous to humans in significant concentrations. Copper is an essential trace mineral for human health, but if an excess of copper is present, a number of complications arise. A high blood concentration of copper is linked to Alzheimer's disease and particular types of cancers such as breast and lung cancer. Acute copper poisoning is very rare but can occur if large amounts are absorbed. This can be fatal as failure of organs such as the liver and kidneys begins to happen.

Is Copper a Metal?

Yes, copper is a metal. It is further considered to be a heavy metal due to its relatively high density. For more information, see our guide on Metalloids.

What Is the Difference Between Copper and Metal?

Copper is one of more than 90 elemental metals. Copper is a metal, but many metals are very different from copper. Other metals are different in their color; most metals are white or gray, but copper is reddish-brown. Other metals can be different in their physical and chemical properties—harder and more brittle than copper, and they do not generally conduct heat or electricity as easily.

What Is the Difference Between Copper and Aluminum?

Copper and aluminum are two different metals with different properties. The most obvious visual difference is the color: copper is a reddish-brown while aluminum is a dull silvery gray. Copper has a higher tensile strength than aluminum and better electrical and thermal conductivity.

What Is the Difference Between Copper and Brass?

Brass is an alloy of predominantly copper and zinc. Brass is therefore different from copper as it includes other metals. Brass can include further metals like tin, lead, aluminum, or manganese in smaller amounts to achieve specific properties.

Summary

This article presented copper, explained what it is, and discussed the various applications of copper. To learn more about copper, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

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Xomety X
Team Xometry
This article was written by various Xometry contributors. Xometry is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding, urethane casting, and more.