Aluminum

Pure aluminum (Al) is a silver-white, malleable, ductile metal with one-third the density of steel. It is the most abundant metal in the earth's crust. Unlike most of the other major metals, aluminum does not occur in its native state, but occurs ubiquitously in the environment as silicates, oxides and hydroxides, in combination with other elements such as sodium and fluoride, and as complexes with organic matter. When combined with water and other trace elements, it produces the main ore of aluminum known as bauxite. Aluminum's dull lustre results from a thin coating of oxygen that forms when it is exposed to air. This characteristic accounts for aluminum's resistance to corrosion. Aluminum is an excellent conductor of electricity and has twice the electrical conductance of copper. It is also an efficient conductor of heat and a good reflector of light and radiant heat.

History

Aluminum metal was first isolated in 1825 by the Danish physicist and chemist Hans Christian Oersted, but an economic method of commercial production was discovered only in 1886 by Charles M. Hall of the US and Paul-Louis Toussaint Héroult of France. Both men were working independently at the time of their discoveries. The world aluminum industry is still based on the Hall-Héroult method of production. Because this process requires large amounts of electricity, smelters are located in those areas, such as Canada, where there is an abundance of electricity at a reasonable cost.

 Combining aluminum with other metals to produce alloys enhances its characteristics and increases its versatility. The most common metals used in combination with aluminum are COPPER, magnesium, manganese, silicon and ZINC. Aluminum's tensile strength, hardness, corrosion resistance and heat-treatment properties improve when alloyed with one or more of these metals. Some copper-aluminum alloys, for example, can exceed the tensile strength of mild steel by as much as 50%.

Bauxite, the main ore of aluminum, contains about 50-60% alumina (aluminum oxide, Al2O3) and is formed by the weathering of aluminum-rich rocks under tropical conditions. Aluminum is produced by separating pure alumina from bauxite in a refinery, then treating the alumina by electrolysis. An electric current flowing through a molten electrolyte, in which alumina has been dissolved, separates the aluminum oxide into oxygen, which collects on carbon anodes immersed in the electrolyte, and aluminum metal, which collects on the bottom of the carbon-lined cell (cathode). On average, it takes about 4 t of bauxite to obtain 2 t of aluminum oxide, which in turn yield 1 t of metal. The word "aluminum" was suggested by Sir Humphry Davy in the early 1800s. It has been retained in North America, but has been modified to "aluminium" in the rest of the world.

In both its pure and alloyed forms, aluminum is used to make a variety of products for the consumer and capital-goods markets. The largest markets for aluminum are transportation, packaging, building and construction, electrical, machinery and equipment, and consumer goods. North America is the largest consuming region, followed by Asia and Europe.

Canadian Industry

The aluminum industry was first established in Canada at the turn of the century in Shawinigan, Qué, when the Northern Aluminum Company (now ALCAN ALUMIN LTD) established its first smelter. Over the next 5 decades, Alcan established a network of smelters and an alumina refinery in Québec and one smelter in BC. Alcan was joined by the Canadian British Aluminum Company in the 1950s when it established a smelter at Baie-Comeau, Qué. The smelter was subsequently purchased by Canadian Reynolds Metals Company, which expanded the smelter's capacity in 1985 and again in 1991. Until 1987, Alcan and Canadian Reynolds were the only primary aluminum producers in Canada. Three more companies, Aluminerie de Bécancour Inc (in 1987), Aluminerie Lauralco Inc (in 1992) and Aluminerie Alouette Inc (also in 1992) were established in the province of Québec, raising Canada's total aluminum capacity to 2 283 000 t. Canada's total primary aluminum production capacity is now rated at over 2 400 000 t annually, valued at $5.5 billion, with production capacity increasing and expected to reach 3 000 000 t by 2005.

Canada does not have any bauxite mines; however, the availability of abundant hydroelectric power at a competitive price, a qualified labour force and modern public infrastructure close to major markets led to the establishment of a world-class aluminum industry in Canada. Canada currently produces primary aluminum from smelters in Québec and Kitimat, BC. Refined metal is fabricated by casting, rolling and extrusion. Manufactured products include doors, windows, house siding, beverage cans, foil products, cooking utensils and electrical wiring.

Canada is the world's fourth largest producer of aluminum, after the US, Russia and China, and the second largest exporting country after Russia. The US is the most important market for Canadian production.

Secondary (Recycled) Aluminum

Secondary aluminum production continues to increase worldwide, attributable to continuing improvements in scrap collection systems and increased recycling rates. Recycling aluminum requires less than 5% of the energy used to make the original metal. The automotive industry is the largest consumer of secondary aluminum, consuming 80% of secondary production either through direct sales or to casters supplying the automotive industry. As requirements for lighter vehicles increase, it is likely that the demand for secondary aluminum will increase significantly.

See also METALLURGY.