Strong, lightweight, and corrosion-resistant, aluminium is one of the most widely used metals in the world. It first gained popularity in the late 19th century and can now be found in everything from packaging and gadgets to cars and buildings.

Even though we use aluminium all the time, most of us don't really know how it's made. Well, that's we at Clickmetal are here to change!

As one of the UK's leading suppliers of custom-cut metal, we're passionate about aluminium and its many uses. Below, we'll walk you through the entire process of how aluminium is made, step-by-step - from extracting the raw materials to turning it into the finished product. Let's get started!

1. Mining the Raw Material (Bauxite)

The process of making aluminium begins with bauxite, a reddish-brown rock that's the main source of aluminium. Bauxite is mostly found in tropical and subtropical areas like Australia, Africa, and the Caribbean. It contains 30 - 60% aluminium oxide along with impurities like silica, iron oxide, and titanium dioxide.

The first step is mining this raw material, usually done through open-pit mining, where the top layers of soil and rock are cleared away to reveal the ore. Once the bauxite is mined, it's taken to a refinery where the real magic of turning it into aluminium starts!

2. Refining the Bauxite (Bayer Process)

The next step in making aluminium is refining bauxite into alumina, or aluminium oxide. This is done using the Bayer Process, developed by Karl Josef Bayer in 1886. Here's a simplified overview of how it works:

  • Digestion: The crushed bauxite is mixed with a hot, concentrated sodium hydroxide (NaOH) solution inside high-pressure tanks. This causes the aluminium oxide to dissolve and form sodium aluminate, while other impurities stay solid.
  • Separation: The mixture is allowed to settle, and the solid impurities are removed. The clear sodium aluminate solution is then cooled and seeded with aluminium hydroxide crystals, which help the aluminium hydroxide form.
  • Precipitation: As the solution cools down, aluminium hydroxide starts to separate out.
  • Calcination: The aluminium hydroxide is filtered, washed, and heated in kilns or calciners at around 1000-1100°C. This removes the water, leaving behind alumina, a fine white powder.

We're almost there, but the alumina still needs to go through one more important process to become aluminium.

3. Electrolytic Reduction (Hall-Héroult Process)

To turn alumina into aluminium, it goes through a process called electrolytic reduction, better known as the Hall-Héroult process. This method was developed independently by Charles Martin Hall and Paul Héroult in the late 1880s. Here's a breakdown of how it works:

  • Electrolysis Setup: The alumina is placed in a large smelting cell filled with a molten mixture of cryolite (Na3AlF6) and aluminium fluoride (AlF3). This mixture helps lower the melting point of alumina and improves conductivity, making the process more efficient.

  • Electrolysis Process: A direct electric current is passed through the cell. At the cathode (the negative electrode), aluminium ions are reduced, forming molten aluminium. Meanwhile, oxygen is released at the anode (the positive electrode), which reacts with the carbon anode to produce carbon dioxide.

  • Collection: The molten aluminium, being heavier than the surrounding liquid, sinks to the bottom of the pot. It's then periodically syphoned off and poured into moulds or cast into ingots, which are cooled and ready for the next steps in production.

And that's how alumina becomes aluminium!

4. Alloying

The liquid aluminium is usually mixed with other elements like silicon, magnesium, copper, manganese, or zinc to improve its strength, resistance to corrosion, and how easily it can be shaped or worked with. The specific elements added depend on what the aluminium will be used for.

5. Casting and Cooling

Once the liquid aluminium has been purified and mixed with other elements, it's shaped into different forms depending on what the final product will be. Some common ways to shape aluminium include:

  • Ingot Casting: Aluminium is poured into large blocks (called ingots) for storage or future processing. These ingots can later be rolled, stretched, or shaped into sheets, foils, or other products.
  • Continuous Casting: Aluminium is continuously poured into moulds, creating long slabs or strips that can be rolled into thinner sheets, often used for things like cans or car parts.
  • Die Casting: Molten aluminium is injected into a steel mould under high pressure to create detailed, accurate shapes. This method is commonly used for car and aeroplane parts.
  • Sand Casting: A sand mould is used to shape the aluminium, which is great for making large parts, such as engine blocks or heavy equipment parts.

After casting, the aluminium cools and hardens. The speed at which it cools can affect its properties: faster cooling can make the metal stronger, while slower cooling allows for more flexibility.

6. Forming and Shaping

Once the aluminium has hardened, it can be shaped into products using different techniques:

  • Rolling: Aluminium blocks or slabs are rolled into thin sheets, foils, or plates. This method is commonly used to make materials for packaging, construction, and cars.
  • Extrusion: The aluminium is heated and pushed through a mould (die) to create long shapes like tubes, rods, or beams. This is often used for making architectural parts and structural components.
  • Forging: Aluminium is pressed with force to shape it into strong, durable parts, which are frequently used for things like aeroplane components.
  • Stamping / Pressing: Thin sheets of aluminium are pressed into specific shapes using a die, a method commonly used to make car body panels and other parts.

7. Heat Treatment

Heat treatment processes like annealing, quenching, or ageing can be used to change the structure of aluminium and make it stronger, harder, or more flexible, depending on what it's needed for. These treatments help improve the metal's overall performance for different applications.

8. Finishing

After aluminium products are shaped, they often get surface treatments to improve how they look and perform. These treatments include:

  • Anodising: This process adds a thicker protective layer to the aluminium, making it more resistant to rust and allowing it to be coloured.
  • Painting or Powder Coating: Used to enhance the appearance and provide extra protection from the elements.
  • Polishing: Gives the aluminium a shiny, reflective finish, either for decoration or practical use.

9. Fabrication

Now for the final step: putting the aluminium parts together to make finished products! This can involve machining, welding, bending, and other techniques to create everything from car and aeroplane parts to building materials and everyday items.

10. Recycling Aluminium (Optional)

One of the best things about aluminium is that it can be recycled over and over without losing its quality. While making new aluminium uses a lot of energy, recycling it only takes about 5% of that energy. This is why more and more aluminium is being recycled after use, helping to make it last longer and reduce environmental impact.

Get Your Aluminium from Clickmetal

Looking for high-quality aluminium products? Clickmetal has you covered. We specialise in precision-cut aluminium sheets, angles, bars, tubes, channels, plate, stair nosings, and more.

Need finishing or fabrication? We also offer a range of processing services (including anodising, polishing, and powder coating) to make your project a breeze.

Check out our full range today!