Aluminum

• Aluminum is the most abundant metal and the third most abundant element in the earth's crust, after oxygen and silicon. It comprises about 8% of our planet's mass.
• Aluminum is a silvery-white metal with many valuable properties. It is light (density 2.70 g/cm³), non-toxic, and can be easily machined or cast. With an electrical conductivity 60% that of copper and a much lower density, it is used extensively for electrical transmission lines. Pure aluminum is soft and brittle, but can be strengthened by alloying with small amounts of copper, magnesium, and silicon.

• Aluminum is too reactive chemically to occur naturally as the free metal. Instead, it is found combined in over 270 different minerals. The chief ore of aluminum is bauxite, a mixture of hydrated aluminum oxide (Al₂O₃·xH₂O) and hydrated iron oxide (Fe₂O₃·xH₂O). Another mineral important in the production of aluminum metal is cryolite (Na₃AlF₆).
• Metallic aluminum was first prepared in 1825; however, because of the high cost of production, aluminum remained a laboratory chemical for many years. In 1886, Charles Martin Hall and Paul Héroult independently discovered and patented the process in which aluminum oxide is dissolved in molten cryolite and decomposed electrolytically. The Hall-Héroult process remains the only method by which aluminum metal is produced commercially.

• Based solely on its chemical reactivity, aluminum should not be very useful at all. Its standard reduction potential is -1.66 volts, indicating that it is a very good reducing agent. It is far more active than iron, which has a reduction potential of -0.44 volt. Aluminum weathers far better than iron, however, because the product of its corrosion, Al₂O₃, adheres strongly to the metal's surface, protecting it from further reaction. This is quite different from the behavior of iron's corrosion product, rust. Rust flakes off the surface of iron, exposing the surface to further corrosion.
• Recycling of aluminum saves considerable energy. Because the aluminum is already in the metallic state, all of the energy spent in purifying the ore and reducing it to the metal is saved when aluminum is recycled. The aluminum needs only to be melted to be reused. Aluminum has a rather low melting point, 660°C, and requires only 26 kJ/mol to melt. To reduce a mole of Al from Al₂O₃ requires over 780 kJ.

• Automotive, Can, and Structural Applications Aluminum is used in four major areas; the automotive industry, cans and other packaging materials, the electrical industry, and for structural applications.
• Aluminum is light, offering a high strength-to-weight ratio so important to industries like transportation, where Alcan is an industry leader in developing new applications.
• Equally important are aluminum's thermal conductivity, versatility and decorative potential, especially for packaging and building products.

• Its high electrical conductivity has long made aluminum a material of choice in the electrical industry.
• For structural applications, aluminum reduces the load demand on foundations in both industrial and residential buildings; it can be anodized or painted, meeting designers' aesthetic needs; and, when extruded, aluminum offers an almost unlimited range of profiles and shapes.

For more information, visit the Aluminium Association of Canada: http://www.aia.aluminium.qc.ca/english/, or the Aluminum Association website: http://www.aluminum.org.