All About Copper
Learn more about this material in full detail and how it can be used in manufacturing.
Copper is a metal and chemical element with excellent electrical and thermal conductivity and good corrosion resistance. It is also easy to shape and has an instantly recognizable 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 as you may remember from high school chemistry. The copper element symbol is Cu, from the Latin “cuprum.” It is a ductile metal with a reddish-brown color. 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, in the eastern Mediterranean Sea as the island was the major source of copper in ancient times. Cuprum was the “metal of Cyprus.”
Copper is typically a reddish-brown color. However, pure copper before oxidation is actually a pink color. The formation of brown copper oxide happens so rapidly that any readily available copper will be the common reddish-brown. Copper can also develop a greenish-blue tarnish over time (such as on the Statue of Liberty)—this is a copper carbonate. Copper is a shiny metal that can be processed into many different practical forms, such as the pipes shown in the image below, as well as plumbing pipes and electronics.
Copper pipes.
A Brief History of Copper
Copper has been a crucial metal in many ancient civilizations, but it is generally agreed that the Mesopotamians discovered copper. A copper pendant that was discovered in Northern Iraq has been dated back to approximately 8,700 BC and is currently thought to be the oldest object made of 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 the few metals that can occur naturally in its native metallic form. This is different from most metals, which 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 Copper Made of?
Pure copper is a chemical element and not an alloy. 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—which are first mined, then 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.
Copper Making Processes
The different processes to make copper are described below:
1. Mining
Mining of copper ores is usually done in large open pit mines which are open holes in the ground that are dug deeper gradually. Explosives are used to blast the rock, and the resulting boulders are transported for crushing into smaller pieces for processing.
2. Extraction
There are two main purification processes for the two common types of copper ore. 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, the pregnant leach solution is sent to a solvent extraction process to concentrate the copper in the solution in a process called “hydrometallurgy.” The 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 in the electrorefining process.
4. Alloying
Copper alloys are made by first melting the alloying material, 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 to remove impurities from the metal. The process is quite expensive and has a very high electrical demand.
Different Types of Copper
Copper is available in different types, and each of these types are best suited 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 a 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 popular because it’s great 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
These are very small particles of copper, or copper-based materials, that are anywhere from 1–100 nm in size. These nanoparticles behave differently than 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
These are the purest coppers available, having very minimal impurities thanks to their non-oxidizing conditions. They are melted under a granulated graphite bath which gets rid of the oxygen. Its high electrical conductivity and low volatile impurities make it suitable for use in high-vacuum electronics.
9. Electrolytic Coppers
To remove impurities, electrolytic coppers are put in a solution and refined by electrolysis. This high-purity grade of copper has high electrical conductivity and therefore is employed in various electrical components such as bus bars and windings.
Copper Materials that Instant Quote with Xometry
Xometry Instantly Quotes CNC machining, sheet cutting, and sheet metal copper projects. Below are some of the materials available for 24/7 pricing and ordering.
- Copper 101 (pure copper)
- Copper 110
There are also brass and bronze variants that use a copper base:
- Copper 260 (brass)
- Copper 932 (bronze)
- Copper 360 (brass)
Copper Properties
The properties of different types of copper are shown in Table 1:
| Copper Type | Composition | Properties | Common Uses | Examples |
|---|---|---|---|---|
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 |
| Copper Type | Density (g/cm3) | Melting Point (°C) | Boiling Point (°C) | Ductility | Thermal 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.
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:
| Copper Type | Reactivity | Oxidation 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.
Copper Applications
The applications of copper are found throughout everyday society. Listed below are some common examples:
1. Electronics
In electronics, copper is commonly used for its 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
Since it’s quite the eye candy (well, for a metal), copper is commonly used in architecture. 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 in the renewable energy industry for, inter alia, wind turbines and solar photovoltaic panels which need copper for connections and cabling.
6. Medical Equipment
Copper’s antibacterial properties make it a firm favorite for medical equipment coatings. In this way, it reduces the risk of infection in patients.
7. Electrical Wiring
Another thing that copper’s brilliant electrical conductivity is useful for is electrical wiring. The cross-section of copper required to carry a particular current effectively is less than other reasonably available materials such as aluminum.
8. Industrial Machinery
Copper is used in the manufacturing of many industrial pieces of 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.
Characteristics of Copper
Copper metal has the primary characteristics of being an excellent electrical and thermal conductor. Since it’s a malleable and ductile material that can be bent relatively easily, it’s easy to work with and preferred for things like flexible cabling. It’s corrosion resistant, even in water and seawater environments, and more aesthetically appealing than other types of metal (it can even be polished to amp up its glam).
The Benefits of Copper
Copper has a number of clear benefits which are listed below:
- Has excellent electrical conductivity, second only to silver, making it the most widely used conductor for electrical and electronic components globally.
- Has very good thermal conductivity, and therefore is used in heat exchangers, such as condensers in refrigeration and air conditioning units.
- Is corrosion resistant, particularly in water and seawater applications, which has led to its widespread usage in plumbing piping for water systems.
- Is ductile and can be bent relatively easily. It is easy to work with in plumbing systems as well as in cabling.
- Is antimicrobial, which can be very useful in water conveyance, as well as in medical applications to protect the health of patients.
The Limitations of Copper as a Manufacturing Material
Copper has a number of limitations, some of which are listed below:
- Is relatively expensive compared to potential alternative materials such as aluminum (electrical cabling) or plastics (water piping).
- Is relatively heavy compared to materials such as aluminum, so for overhead wires, it may not be practical.
- Oxidizes, particularly at high temperatures, and so has a limited life span if exposed to air.
- Presents a shock risk compared to the alternative signal transmission technology of fiber optics.
- Is toxic in large amounts, so it cannot be applied where regular ingestion of copper could occur, such as in utensils.
Common FAQs About Copper
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 will form on the surface (think, Statue of Liberty) as the copper oxide reacts with water and carbon dioxide in the air.
What Type of Metal is Copper?
Copper is 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 Aluminum?
The most obvious visual difference between the metals copper and aluminum is the color; copper is a reddish-brown while aluminum has a dull silvery gray hue. Also, copper has a higher tensile strength than aluminum and better electrical and thermal conductivity.
What is the Difference Between Copper and Brass?
Brass and copper differ in that brass is an alloy usually made up of copper and zinc, whereas copper just has copper in it. Other than zinc, brass can also contain other metals like tin, lead, aluminum, or manganese in smaller amounts, depending on the properties needed.
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