See all Blog Posts How Aluminum is Made? Category: Aluminum Posted: October 15, 2015 In many ways, aluminum is the perfect metal. It is strong, light, resistant to heat and corrosion, and a good conductor of electricity. It is also 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. However, it was not until 1809 that English chemist Sir Humphry Davy formally identified and named it. Today, 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 at its 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. What is Aluminum Made Of? In its pure elemental form, aluminum is composed entirely of aluminum atoms arranged in a crystalline structure. This gives the metal its characteristic properties, including lightweight, high strength-to-weight ratio, excellent corrosion resistance, and good thermal and electrical conductivity. However, in practical applications, aluminum is often found in alloyed forms. Aluminum alloys are made by combining pure aluminum with small amounts of other elements, such as: Copper (Cu): Improves strength and hardness. Magnesium (Mg): Increases strength while maintaining light weight. Silicon (Si): Enhances fluidity in casting and increases strength. Manganese (Mn): Improves corrosion resistance and adds strength. Zinc (Zn): Increases strength and improves machinability. These additional elements are usually added in small percentages, but they significantly modify the properties of aluminum to suit various engineering and manufacturing needs. What is aluminum made of will depend on the application for which it is being used. Where Does Aluminum Come From? So, where does aluminum come from? Aluminum is derived from the ore bauxite, which is the primary source of aluminum around the world. Bauxite is primarily composed of aluminum oxide minerals such as gibbsite, boehmite, and diaspore. The process of extracting aluminum from bauxite involves two main steps: Bayer Process for How to Make Aluminum In this process, bauxite ore is first crushed and then mixed with a hot solution of sodium hydroxide. This dissolves the aluminum oxide component of the bauxite, forming a soluble sodium aluminate solution. The other impurities, called red mud, settle to the bottom and are removed. Dissolved aluminum hydroxide is then precipitated out of the sodium aluminate solution by cooling or seeding with aluminum hydroxide crystals. The precipitate is filtered and then heated in a kiln to produce alumina, a white powder. Hall-Héroult Process for How to Make Aluminum The alumina produced is then subjected to electrolysis to extract aluminum metal. This process involves dissolving the alumina in molten cryolite inside an electrolytic cell. When an electric current is passed through the cell, aluminum metal is deposited at the cathode, while oxygen is released at the anode. The aluminum metal is collected and often cast into ingots or other forms for further use. Together, these processes enable the transformation of raw bauxite into aluminum metal. 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, a rock containing about 52% aluminum oxide with impurities of iron oxide, silica, and titania. Bauxite is commonly found in deposits on or close to the Earth’s surface throughout many parts of the world, including Europe, Asia, Australia and South America. Mining Aluminum Geologists locate bauxite deposits by taking samples and conducting investigatory drilling. When deposits are found, they are mined in open pits. The Earth is blasted loose, and the bauxite is extracted using power shovels or draglines. 90% of all mined bauxite is made into alumina to be smelted into aluminum. The remaining 10% is used for other purposes, including the manufacture of abrasives, furnace linings, and proppants for the oil industry. It takes 4 tons of high-quality bauxite to produce 2 tons of alumina, from which 1 ton of aluminum can be made. Refining the Bauxite Bauxite is refined using the Bayer process, which was first developed by Karl Joseph Bayer in 1888. The Bayer process has four steps: digestion, clarification, precipitation, and calcination. Digestion The bauxite is ground, mixed with caustic soda, and pumped into pressure tanks where steam heat and pressure are applied. This causes the caustic soda to react with the aluminum compounds in the bauxite to form a solution of sodium aluminate. The unwanted impurities are left behind in what is known as red mud. Clarification Next, the sodium aluminate solution is passed through blow-off tanks where the pressure is reduced to atmospheric pressure. The red mud is removed using clarifying agents and cloth filters. The clarified solution is then cooled in heat exchangers and pumped into tall silos. Precipitation Aluminum hydroxide seed crystals are added to the sodium aluminate solution to cause precipitation. During this process, the aluminum becomes solid. This results in large aluminum crystals, which are filtered and washed to remove water and other impurities. Calcination Now, the aluminum hydroxide crystals are subjected to calcination, a thermal treatment process in which the air supply is controlled. Rotary kilns heat the crystals to over 960° C, removing any remaining impurities and leaving a fine white powder known as alumina or aluminum oxide. Aluminum Smelting Smelting is the process during which aluminum is extracted from the alumina. This is carried out by the Hall-Héroult process, which was invented in 1886 by Charles Martin Hall and Paul Héroult. The smelting takes place in steel reduction pots filled with molten electrolytes, 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 moulds to form foundry ingots. At this stage, it’s 99.8% pure. It can be further refined to produce superpure aluminum or alloyed with other metals. Superpure Aluminum Superpure aluminum of high purity (99.99%) is soft and lacks tensile 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. Aluminum Alloys 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). Recycling Aluminum Aluminum can be endlessly recycled without losing its quality. This makes it one of the most environmentally friendly metals on the planet. Most of the aluminum ever produced is still being used today. 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