Ferrous metals vs non-ferrous metals

What is the difference between ferrous metals and non-ferrous metals?

Before we explore the different properties and characteristics of ferrous and non-ferrous metals, it’s important to understand the fundamental difference between the two; ferrous metals are metals that contain iron, while non-ferrous metals do not.

Generally speaking, ferrous metals are cheaper to source and produce, although they corrode much more easily than non-ferrous metals. Barring a few exceptions, ferrous metals are magnetic, a property often used to identify and separate ferrous and non-ferrous metals, for example for scrap or recycling.

Whilst iron and steel are commonplace now, humans worked with non-ferrous metals such as copper, tin, bronze, lead and many precious metals for many thousands of years until somewhere around 1500BC, commonly referred to as the Iron Age.

Ferrous metals.

The category of ferrous metals contains a number of iron alloys and types of steel, all of which are generally heavier, stronger and more durable than non-ferrous metals. Ferrous metals are found throughout manufacturing, construction and architecture in bridges, railroads, high-rise buildings and almost endless applications.

Ferrous metals are vulnerable to rust due to their iron content, and often need to be treated or protected to avoid this by polishing,  surface treating, or using appropriate metal paints and primers.

Ferrous metals are also generally magnetic, allowing for quick identification and sorting by simply sifting through scrap or other metal with an extremely powerful industrial magnet.

Recycling ferrous metals is a complicated process, involving many steps including melting, reforming, recasting and purifying; however it is still a cheaper and more environmentally friendly option than extracting more raw ore.

By far the most widely used ferrous metal is steel.

Stainless steel.

Stainless steel is a shiny, smooth alloy containing chromium, nickel, and manganese, with an aesthetically pleasing silver appearance. It is an unusual ferrous metal in that it is actually highly corrosion resistant due to its chromium content, meaning it is often used in culinary or surgical environments where hygiene is key.

Carbon steel.

Carbon steel is extremely hard and strong, usually made from over 90% iron. High carbon steel is widely used in construction and manufacturing, in girders, structural shapes, tools, machinery parts and gears.

Wrought iron.

Wrought iron is actually highly corrosion-resistant due to its low carbon content and is used in many scenarios, including agriculture, gates and fences, and other outdoor decorative items.

Cast iron.

Cast iron is hard, brittle, wear-resistant, and heat-resistant, and widely used in cookware, engines, automotive parts, pipes, and stoves.

Non-ferrous metals.

As we have established, almost every pure metal and any alloy not containing iron is non-ferrous, meaning they all have different characteristics, properties and uses. However, they do generally share some similarities.

Because non-ferrous metals do not contain iron, they cannot rust, as rust is only formed when oxygen reacts with iron. However, this does not mean they are unaffected by other forms of corrosion. Aside from a couple of rare exceptions, non-ferrous metals are also non-magnetic, as iron is the only ferro-magnetic metal. Sometimes people believe that copper or brass are magnetic due to some coins in the UK being attracted to magnets; however, these are actually made from plated steel.

Many non-ferrous metals are highly malleable, meaning they can be reused and reshaped without degrading or loosing their valuable chemical properties. It is possible to recycle most non-ferrous metals multiple times, meaning they are often a more environmentally friendly, economical, and energy-saving option.

There are very few non-ferrous metals that can compete with steel or iron in terms of tensile strength or ability to bear weight or resist force. Those that do share some of these properties, such as tungsten or titanium, tend to be prohibitively expensive and impossible to use in the quantities required for large-scale construction or industrial applications.

It is important to note that some non-ferrous alloys may contain an insignificant amount of iron, but not enough for them to share any properties of ferrous metals and therefore be categorised as such.

Aluminium.

Aluminium is a highly versatile metal with a great strength-to-weight ratio. Aluminium is great at resisting corrosion, and is often found in marine applications, aerospace engineering, automobiles and many home appliances and every-day items such as cans and cookware.

Copper.

Copper is one of the most successful conductors of electricity and heat, and is extremely ductile and malleable. Copper is commonly used for wires and other electrical components as well as roofing, piping and some machinery. Bronze and brass are alloys of copper.

Zinc.

Zinc is highly corrosion resistant and has a low melting point, usually used as a rust-preventative protective coating applied to steel through a process called galvanising.

Precious metals.

Gold, silver and platinum are all non-ferrous metals, and are most commonly used for jewellery or other decorative purposes.

Other metals.

There are in fact a few magnetic non-ferrous metals, including nickel and cobalt. Other non-ferrous metals include lead, tin, mercury and lithium.