Non-ferrous metals were the first metals used for metallurgy by humans. Copper, gold and silver were all attractive materials for early humans, especially since these metals were not as susceptible to corrosion as ferrous metals.
Copper was the first metal to be forged and shaped into objects (during the ‘Copper Age’), while gold, silver and copper all replaced wood and stone for some early applications since they could be fashioned into a variety of forms. The rarity of these metals meant they were often used for luxury items. Creating bronze, by alloying copper with tin, led to the Bronze Age, which followed the Copper Age.
Non-ferrous scrap metals are usually recycled and have formed an important part of the metallurgy industry, where new metals are produced using scrap materials. This can include re-smelting and re-casting non-ferrous metals. Recycled non-ferrous metals are sourced from industrial scrap materials, scrapped technologies (such as copper cables) and even particle emissions.
Non-ferrous metals are used for a wide range of commercial, industrial and residential applications. This may require careful material selection according to their mechanical properties, including how easily the metal can be shaped and whether these properties will be altered in the process.
Many of the properties of ferrous metals can be found in non-ferrous materials, for example, aluminium or titanium alloys can replace steel in some instances, and the magnetic properties of iron can be emulated by cobalt, nickel or rare earth elements that have been alloyed.
However, because non-ferrous metals are often more expensive they tend to be used for their unique attributes rather than simply as a replacement for steel. These attributes include lighter weights, conductivity, corrosion resistance and non-magnetic properties. Non-ferrous metals also tend to be softer and more malleable than ferrous metals, meaning they can also provide aesthetic applications, as with gold and silver.
The properties of non-ferrous metals include:
- Easy to fabricate (including machinability, casting, and welding)
- High corrosion resistance
- Good thermal and electrical conductivity
- Low density
- Non-magnetic
- Colourful
Metals, both ferrous or non-ferrous, can be cast into the finished part or cast into an intermediate form like an ingot before being extruded, forged, rolled, wrought or worked into the desired shape. The reaction to non-ferrous metals to these processes is more severe than with ferrous materials, meaning that the properties of cast or wrought forms of the same metal or alloy may differ.
It is important to choose the right metal to balance performance with aesthetics as this may influence production methods. While ferrous metals tend to be chosen for castings, non-ferrous metals can also be chosen for properties such as corrosion resistance, lack of magnetism or weight rather than tensile strength. Materials like bronze or brass may also be chosen for appearance or tradition.
Because they include any metal that doesn’t include iron, there are lots of different non-ferrous metals and alloys. Here are some of the properties and common uses of some of the more common non-ferrous metals:
1. Copper
Having been used by humans for thousands of years, copper is still widely used by industry. The addition of copper alloys, brass (copper and zinc) and bronze (copper and tin) have widened the uses for this non-ferrous metal further (see below for detail on these alloys).
The properties of copper and its alloys include high thermal conductivity, high electrical conductivity, good corrosion resistance, and high ductility.
These properties have allowed copper and its alloys to be used for heat exchangers and heating vessels, as an electrical conductor in wiring or motors, as a roofing material, for plumbing fittings, as well as for saucepans and statues.
Copper also oxidises to a green colour.
2. Aluminium
Aluminium is an important metal that is used in a wide range of applications due to its low weight and ease of machining. Despite being a relatively expensive material, aluminium is also the base metal for many alloys.
Being corrosion resistant and a good conductor of heat and electricity (albeit less so than copper), as well as having good ductility and malleability, aluminium can require annealing as it becomes hard following cold working.
The light weight of aluminium makes it perfect for aerospace and automotive applications as well as for marine use in yachts. Aluminium is also found in bicycle frames, saucepans and drink cans.
3. Lead
Lead has been used over the centuries for a range of applications, including for bullets, in fuels and even in paint. However, it was found to be unhealthy when released into the atmosphere, while other applications also caused harm to users.
Lead is the heaviest common metal and is resistant to corrosion. It also doesn’t react with many chemicals and is soft and malleable.
Although many of its former uses are no longer allowed, lead is still widely used for batteries, power cables, and acid tanks.
4. Zinc
Zinc has been used for centuries as an alloying element, particularly to alloy steel for a range of purposes as well as alloying copper to create brass.
Galvanising materials with alloying elements offers them a greater resistance to rust, affording it uses for chain-link fencing, guardrails, suspension bridges, lampposts, metal roofs, heat exchangers, and car bodies. Zinc is also used as a sacrificial anode in cathodic protection (CP) and as an anode material for batteries. Zinc oxide is also used as a white pigment in paints and to disperse heat during rubber manufacture.
5. Silver
Silver has been used as a precious metal for centuries. With the highest electrical conductivity, thermal conductivity and reflectivity of any metal, silver is also soft and malleable when heated and is highly resistant to corrosion.
Used for jewellery and currency, silver can also be found being used in solar panels, for water filtration, in electrical contacts and conductors as well as for stained glass and even in specialised confectionary.
6. Gold
Another precious metal that has been used for jewellery and coinage, gold is the most malleable of metals as well as being ductile and resistant to corrosion and many other chemical reactions.
Its electrical conductivity has seen gold used in computer devices as well as for infrared shielding, for the production of coloured glass, for gold leaf and also for tooth restoration.
7. Titanium
Titanium was first discovered in 1791 and offers good corrosion resistance and the highest strength-to-density ratio of any metallic element. Unalloyed, it is as strong as some steels yet less dense.
It can be alloyed with metals including iron and aluminium to create strong yet lightweight alloys for aerospace, automotive, agricultural, military, medical, and sporting uses as well as being used for jewellery and mobile phones.
Alloys mix a metal with an element to improve the properties or aesthetic, such as with brass, which is a mixture of copper and zinc. Alloys can be either ferrous or non-ferrous in nature although non-ferrous metals may require a finish as protection or to improve the appearance of an alloyed product.
Common non-ferrous alloys include bronze and brass, which have been cast since the Bronze Age. These alloys melt at lower temperatures than ferrous materials and cast well, making them ideal for decorative applications. Despite being softer than steel, bronze and brass are both corrosion resistant, even in the presence of salt, and so are widely used for fittings on boats. Brass is also resistant to ‘galling,’ when the metal wears against itself. This means that brass can also be used for mechanical parts and machined to create items including locks, bearings and zippers. Bronze is harder than brass, although both are quite expensive as they rely on copper. Brass is created as an alloy of copper and zinc, while bronze is an alloy of copper with aluminium and/or nickel.
People have been using various non-ferrous metals for different uses for thousands of years. The applications for these versatile materials range from decorative uses through to electronics, aerospace and beyond.
Non-ferrous metals, while able to mimic the attributes of some ferrous metals, are usually chosen for their own unique attributes. These attributes include light weight, non-magnetic properties and corrosion resistance. These metals also tend to be more malleable than ferrous metals, allowing them to be used for decorative purposes, such as in jewellery or for making statues.