Aluminium (Aluminum) is the most abundant metallic element in the earth’s crust; aluminum wasn’t discovered or named until 1825. Is a highly reactive metal, which means that it easily undergoes chemical reactions with other elements or compounds in order to form various substances. As a consequence, almost all the aluminum atoms that are naturally occurring on the Earth are hidden in the molecules of more than 270 different minerals, including precious stones, such as emeralds or rubies.
Even if it represents 8.2% of the earth’s crust, which makes it the most common metal and the third most common element in the world, we wouldn’t have known was there without a practical chemistry investigation.
The search commenced in the middle 1700s, when chemists began experimenting with a class of abundant chemical compounds, such as potassium aluminum sulfate (potassium alum), which was known even by the ancient Greeks. Chemical investigation of these compounds suggested there is also an unknown metal in their composition.
The major problem of 18th-century chemists was that they had no way to separate the unknown element from the rest of the atoms in the compounds. In 1825, Danish chemist Hans Christian Ørsted devised a chemical reaction that would extract the element, but his process only was able to produce small amounts, making extremely difficult extensive experiments.
As a result of Ørsted’s finding, German chemist Friedrich Wohler has developed a more effective process, and in 1845 he had produced enough aluminum to demonstrate its basic properties. Even so, the extraction method was still troublesome and slow to support wide-scale production.
In 1854, French chemist Henri Étienne Sainte-Claire Deville has improved the process, dropping the price of aluminum from 1,200 dollars per kilogram to 40 dollars. However, the aluminum was still expensive. But this was about to change during the 1880s, thanks to two major technological leaps.
In 1886, American chemist Charles Martin Hall and French chemist Paul L.T. Héroult independently invented a process for obtaining aluminum from aluminum oxide. The Hall-Heroult process relies on electrolysis, a means of breaking down chemical compounds into component elements using electricity. Each terminal attracts and repels charged atoms (ions). The positively charged anode attracts negative ions and repels positive ions, and the cathode vice versa.
Scientists had tried to produce aluminum through electrolysis since the early 1800s, but without success. Hall and Heroult’s breakthrough was first dissolving aluminum oxide in molten cryolite. Applying an electric current to this material draws the positive aluminum ions to the cathode, which is typically the vat itself, made from iron lined with graphite.
In 1888, Austrian chemist Karl Josef Bayer found a way to extract aluminum oxide from bauxite, a naturally occurring ore easily found in layers just below the Earth’s surface. Australia leads global bauxite mining, producing one-third of the total ore.
Together, both the Hall-Heroult process and the Bayer process (both still in use) inaugurated what could be called the “Aluminum Age”. The metal properties made it an immediate success. It’s lightweight (about a third the weight of steel) but still strong. It’s also very ductile, which means it’s easy to draw into a wire or flatten into a sheet, and it’s malleable, making it relatively simple to bang it into any shape. If we add the fact that it’s an exceptional conductor of heat and electricity, we have an incredibly versatile material.
However, aluminum’s greatest quality may be its resistance to corrosion. Like iron, aluminum is highly reactive to oxygen in the air, but the result of the oxidation reaction is quite different. Oxygen and iron react by producing a layer of rust, while the oxidation of aluminum reaction produces a hard transparent oxide compound that surrounds the aluminum, acting as a shield that protects it from oxygen and other elements. If this protective layer happens gets damaged, it will very quickly reform, reconstructing the shield.
Most aluminum products are actually made from an aluminum alloy. The combination accentuates and amplifies certain properties. For example, alloying aluminum with copper improves strength, while an alloy of aluminum and manganese improves corrosion resistance.
Aluminum can be converted into a variety of products through a series of manufacturing processes. You can cast it into any shape that you want by pouring it into a mould. It can be stretched into thin sheets up to 0.15 millimeters thick. Screws, bolts, hardware and even very thin wire can also be produced.
Another major superpower of aluminum is recyclability. Recycling programs use old aluminum cans to make new ones, at about 30 per cent the cost of making them from scratch. Old cans are torn into pieces and then melted; rectangular blocks are formed, which are then processed into thin sheets, from which new cans are cut. Thanks to this recycling process, two-thirds of the aluminum ever produced is still in use.
How it’s made aluminum: