Aluminium

Aluminium is the most abundant metal in the Earth's crust and one of the most widely used structural metal in the modern world, only after Mild Steel. Its low density (approximately one third that of steel) combined with good corrosion resistance and reasonable strength makes it the dominant material in aircraft construction, vehicle bodywork, packaging, and electrical transmission lines. However, aluminium production is uniquely energy-intensive: the Hall-Héroult electrolytic smelting process, which dissolves alumina in molten cryolite and passes a massive electrical current through the bath, consumes roughly 15 kilowatt-hours of electricity per kilogram of aluminium produced. No other common metal demands anything close to this energy input, making aluminium smelting inseparable from access to cheap, large-scale electrical power.