Aluminium production relies on transforming Bauxite ore ($Al_2O_3 \cdot 2H_2O$) through a dual-stage chemical process. First, the Bayer Process uses a sodium hydroxide solution at 150°C to 200°C to extract pure Alumina. Then, the Hall-Héroult electrolysis reduces this Alumina in a 960°C cryolite bath, consuming 13,000 kWh per tonne. Globally, over 64 million tonnes are produced annually, with 75% of all aluminium ever made still in circulation due to its 95% energy-saving recycling efficiency.
Every soda can or aircraft wing begins as Bauxite, a rock containing 30% to 60% aluminium oxide. To understand what is aluminium made of, we look at its raw chemical state, where the metal is trapped behind oxygen atoms and silica impurities. This raw ore is crushed and mixed with a caustic soda wash that dissolves the alumina while leaving behind iron oxides, often called “red mud.”
Approximately 2 tonnes of bauxite are needed to produce just 1 tonne of alumina, illustrating the significant volume of material processed in these early refinery stages.
The refinery heating cycle must reach 1,100°C to drive off chemically combined water, resulting in a fine white powder. This powder is alumina ($Al_2O_3$), which serves as the direct feedstock for the smelting process that creates the metallic version. The transition from powder to liquid metal requires a specialized environment because aluminium has an extremely high affinity for oxygen.
By 1886, two inventors independently discovered that dissolving alumina in molten cryolite ($Na_3AlF_6$) allowed electricity to break the oxygen bonds. The smelting “pot” operates as a giant battery where carbon anodes are consumed at a rate of 450 kg per tonne of aluminium produced. This electrical intensity is why smelters are often built near hydroelectric dams or massive power grids.
| Material Requirement | Quantity per Tonne of Al | Function |
| Alumina | 1,930 kg | Base raw material |
| Carbon Anodes | 430 – 460 kg | Conducts electricity |
| Cryolite | 10 – 25 kg | Solvent/Electrolyte |
| Electricity | 13,000 – 15,000 kWh | Breaks chemical bonds |
Electrolysis cells run at a low voltage, typically 4 to 5 volts, but utilize currents exceeding 300,000 amperes. At the bottom of these pots, liquid aluminium collects with a purity level of 99.7% or higher. Siphons remove the liquid metal every 24 hours, transferring it to holding furnaces where specific alloys are created.
Standard 6061 alloy adds approximately 1.0% magnesium and 0.6% silicon to the pure aluminium to increase structural strength by over 200%.
The density of this finished metal is 2.70 $g/cm^3$, roughly one-third the weight of steel. This lightness is the primary reason why 80% of modern aircraft airframes consist of aluminium alloys. Engineers favor these materials because they form a natural oxide layer 2.5 to 5 nanometers thick that prevents further corrosion.
In a typical production year, secondary or recycled aluminium accounts for nearly 30% of the total global supply. This shift toward circularity exists because melting scrap requires only 5% of the initial energy compared to the Bayer and Hall-Héroult stages. A used beverage container can be recycled and returned to a store shelf in as little as 60 days.
The thermal conductivity of aluminium is 235 W/m·K, making it the primary choice for heat sinks and high-voltage transmission lines. Even though copper is a better conductor, aluminium provides two times the conductivity of copper on a per-kilogram basis. This efficiency drives the installation of millions of miles of aluminium wiring across global power grids.
17% of global aluminium goes into the construction industry for window frames and facades.
26% is consumed by the transport sector for engine blocks and body panels.
12% is utilized in machinery and high-tech equipment manufacturing.
Since the first industrial applications in the 1850s, the extraction methods have shifted toward reducing carbon footprints. Modern inert anode technology aims to replace carbon with materials that release pure oxygen instead of carbon dioxide. If fully implemented, this could remove millions of tonnes of $CO_2$ from the yearly atmospheric load.
Testing on inert anodes in 2021 showed a potential to reduce direct greenhouse gas emissions from the smelting process by 100%.
Managing the “red mud” byproduct remains a focus for environmental researchers, as 1.5 tonnes of residue are created for every tonne of alumina. New techniques involve using this mineral-rich waste in cement production or as a soil conditioner. Such innovations ensure that the extraction of what is aluminium made of becomes a closed-loop system over the next few decades.
Current smelting technology achieves a current efficiency of 95%, meaning very little electricity is lost as heat. This level of precision allows for the production of specialized 5000-series alloys used in marine environments. These alloys contain 3% to 5% magnesium, providing the necessary resistance to salt-water corrosion for high-speed ferries and hulls.