In many ways, aluminum is the perfect metal. It is strong, light, resistant to heat and corrosion and a good conductor of electricity. On top of that it is plentiful and inexpensive.
Aluminum is also the most abundant metal in the Earth’s crust, and the third most abundant element after oxygen and silicon. Aluminum is the most commonly used metal in the world after iron and steel. Aluminum is a vital component of almost every part of our lives, from the vehicles we drive to the packaging of our food.
Aluminum is most versatile when it’s combined with other metals to form aluminum alloys. The alloying process gives aluminum improved properties to suit a range of applications.
How Aluminum Is Made
Aluminum is made in the following stages:
- Finding the Aluminum Ore
- Mining Aluminum
- Refining the Bauxite
- Aluminum Smelting
Finding the Aluminum Ore
Aluminum tends to combine with other elements and rarely exists in nature in its pure metallic form. Aluminum compounds are found in most common rock types including clay, slate, shale, granite and anorthosite.
The most important aluminum ore is bauxite. Bauxite is commonly found in deposits on or close to the Earth’s surface.
Geologists locate bauxite deposits by taking samples and conducting investigatory drilling. When deposits are found, they are mined in open pits. 90% of all mined bauxite is made into alumina to be smelted into aluminum.
Refining the Bauxite
The bauxite is refined using the Bayer process. The Bayer process has four steps: digestion, clarification, precipitation and calcination.
Smelting is the process during which aluminum is extracted from the alumina. The smelting takes place in steel reduction pots filled with molten electrolyte, where carbon anodes are used to pass an electric current through the electrolyte. Alumina is then added to the molten surface. The electric current deposits molten aluminum which can be collected and siphoned off.
The molten aluminum is then poured into molds to form foundry ingot. At this stage it’s 99.8% pure. Now it can be further refined to produce superpure aluminum or used for alloying with other metals.
Superpure aluminum of high purity (99.99%) is soft and lacks strength. However, it is corrosion-resistant and an excellent conductor of electricity. Superpure aluminum is used in chemical equipment, electronic components, and to make gasoline.
Most aluminum is alloyed with other elements. By alloying the aluminum, its hardness and strength can be significantly improved. Common aluminum alloys are aluminum-manganese (used in beverage containers), aluminum-magnesium (used in appliances and utensils), aluminum-magnesium-silicon (used in buildings and vehicles), and aluminum-copper (used in aircraft).
Aluminum can be endlessly recycled without losing its quality. This makes it one of the most environmentally friendly metals on the planet. Incredibly, most of the aluminum ever produced is still being used today.
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