Aluminium

Aluminum is the most abundant metal in the Earth’s crust and the third most abundant element after oxygen and silicon. Its high affinity for oxygen, which keeps it in a combined state in ores, long prevented its extraction in metallic form. Its industrial production did not begin until the 19th century, with the mastery of electrolysis. Global production, which reached nearly 73 million metric tons of primary metal in 2024, ranks it first among non-ferrous metals and second among all metals, behind steel.

Its production involves two steps: the extraction of alumina from bauxite, followed by the electrolysis of this alumina to obtain the metal. When exposed to air, aluminum develops a thin layer of alumina that protects it from oxidation. Its light weight and resistance to corrosion—qualities sought after in the aerospace and transportation industries—explain its industrial significance. Its density, approximately one-third that of steel, classifies it among the light metals. The addition of elements that form solid solutions with it gives it mechanical strengths comparable to those of hardened steels. Depending on whether they act as a primary additive, a secondary additive, or a simple impurity, these elements significantly alter the characteristics of the final alloy.

The properties required for specific applications are then adjusted through heat and mechanical treatments (structural hardening, quenching, tempering, aging, work hardening) selected according to the desired performance characteristics. The metal is suitable for all metalworking and casting processes, accepts numerous surface treatments—including anodizing and powder coating—and welds easily when the assembly is homogeneous. It is also recyclable without any loss of properties; its recycling consumes only about 5% of the energy required to produce virgin metal—a key advantage given current decarbonization goals.