Aluminium vs Steel:Stepping through the physical properties of one of the industry’s most precious metals

While aluminium has a long history as being a premium and quality product, it hasn’t always been prized for the physical properties that the construction industry finds so beneficial and useful today.

Despite being one of the most abundant elements – by mass – in the earth’s crust, aluminium was historically so difficult to extract that it was rendered extremely rare. Its value as a precious metal exceeded that of gold! Legend has it that Napoleon III would eat using aluminium dinnerware, while his guests were left to make do with gold.

Fast-forward to the 1880s and aluminium became more commercially viable to extract. This is when its first foray into the construction industry was made – in structures like the glinting dome on the church of San Gioacchino in Rome and the construction of the Empire State Building. However, even then (and as these architectural uses attest), it was still a novel and luxurious material.

Aluminium today

Moving forward even further along the timeline and the last few decades have seen aluminium take enormous strides as an important and sought-after structural construction material. As its employment for a diverse range of purposes attests, aluminium has come to be prized for its unique chemical and physical properties, as well as its production lifecycle.

In fact, many of aluminium’s qualities offer up significant advantages over other more established traditional building materials like steel. So, let’s take a look.

Aluminium is versatile

Aluminium is one of the most versatile metals in use today. On average, it is nearly one third of the density of steel – lending itself to use as a lightweight alternative for many construction components traditionally made with steel. For example, aluminium is favoured in the ship-building industry because it offers weight savings of up to 40%.

Aluminium is strong

Not only that, aluminium has a high strength-to-weight ratio. When alloyed with small amounts of other metals, such as magnesium or copper, it is comparable in strength to steel at a fraction of the weight.

Copper alloys are used in airplane manufacturing for their high strength and lightweight properties. In building construction, aluminium allows architects the opportunity to minimise the dead load on supporting structures without compromising the strength of the building as a whole – a key consideration for roofing and cladding applications.

Aluminium is flexible

Aluminium is also more malleable and ductile than steel. It can be spun into more intricate shapes without cracking or rupturing, which makes it suitable for making many different construction components, across a wide array of manufacturing contexts. It is also one of the few metals that can be cast using any metal casting process, including die casting, permanent mould casting, and sand casting, so it’s extremely versatile.

Aluminium is self-protecting

Metal oxidises when it comes into contact with oxygen or other ambient oxidising agents. Iron produces ferric oxide, or rust, which is porous – whereas aluminium produces aluminium oxide, which is impermeable and acts as a barrier to further corrosion.

While steel needs to be galvanised to create a protective surface layer, scratches or damage will expose the steel underneath and invite corrosion. Conversely, if the surface of aluminium is damaged or the oxide layer removed, a new layer will naturally form to prevent any further corrosion.

Aluminium lasts longer

When corrosion does occur, the average rate of penetration for corrosion of aluminium is as low as 0.00051MM/year compared to steel, which can be as high as 0.0445mm/year. These numbers may seem miniscule, but the impact is significant. Evidence from the shipbuilding industry shows that the aluminium alloys used to construct ocean-going vessels corrode roughly 100 times more slowly than their steel counterparts.

For a deeper dive into the showdown between aluminium and steel, download our full ebook where we’ve more extensively put these two metals toe to toe.


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