ALUMINUM
ALUMINUM, the most useful of the nonferrous metals, was first isolated in metallic form in 1825 by Hans Christian Oersted in Denmark. The metal remained a laboratory curiosity until 1854, when Henri Sainte-Claire Deville discovered a process using metallic sodium as a reductant that led to the first commercial production of aluminum. The price of the metal fell from $545 per pound in 1852 to $8 in 1885, and uses for the lightweight metal began to increase greatly. Emperor Napoleon III of France, for example, considered outfitting his army with lightweight aluminum armor and equipment, but the price of the metal remained too high for widespread use.
In 1886, an American, Charles Martin Hall, and a Frenchman, Paul Héroult, independently discovered that aluminum could be produced by electrolyzing a solution of aluminum oxide in molten cryolite (sodium aluminum fluoride). The electrolytic process won immediate acceptance by the commercial industry and in 2002 remained the sole commercial method used for making aluminum.
Hall's invention led to the formation of the Pittsburgh Reduction Company in 1888. This company, now known as Alcoa (for Aluminum Company of America), initially produced fifty pounds of aluminum per day, becoming by the turn of the twentieth century the world's largest producer of aluminum, a position it still enjoys in 2002. A more diverse aluminum industry developed in Europe. Within ten years, firms operated in Switzerland, Germany, Austria, France, and Scotland—all having obtained rights to Héroult's patents to make the metal. By 1900 total world production was about 7,500 short tons; American production was 2,500 tons.
The advent of the airplane in World War I greatly increased demand for the lightweight metal. In 1918 the primary capacity in the United States had grown to 62,500 short tons; world production amounted to 143,900 tons. Steady growth of the aluminum industry continued, and in 1939 the United States produced 160,000 tons of the 774,000 tons produced worldwide. The airplane became a key factor in waging World War II, and aluminum production throughout the world tripled; in the United States it grew sixfold. Another major period of growth in the industry took place during the Korean War, when the United States produced almost half of the world total of 3,069,000 tons. In 1972 total world production of aluminum came to some 12 million tons, but the American share, produced by twelve companies, had dropped to 34 percent, or 4,122,000 tons. By 2000, the aluminum industry in the United States operated more than three hundred plants in thirty-five states, employed more than 145,000 people, and produced an average of 11.5 million tons of aluminum annually.
Aluminum is the most abundant metallic element in the earth's crust. It is made from the mineral bauxite (hydrated aluminum oxide), which is found in plentiful supply throughout the tropical areas of the world. Five countries, Jamaica, Surinam, Guyana, Guinea, and Australia, mined about 61 percent of the world's supplies in 1972, with the remainder coming from twenty-two other countries. At the end of the twentieth century, the U.S. aluminum industry relied to a roughly equivalent degree on production from domestic ore materials (34.3 percent of production in 2000), imported ingots and mill products (33.5 percent), and recycled scrap materials (32.2 percent).
The great growth in the use of aluminum metal indicates its versatility. It has a unique combination of useful properties: lightness, good thermal and electrical conductivity, high reflectivity, malleability, resistance to corrosion, and excellent tensile strength in alloyed form. It is extensively employed in building and construction, where each new house uses almost four hundred pounds of the metal for such items as windows, doors, and siding. Another major market is transportation: the average automobile uses almost eighty pounds of aluminum, and truck and railroad car bodies use aluminum extensively because each pound of weight saved permits an extra pound of revenue-producing payload. The aerospace industries are also large consumers of aluminum. There are many electrical applications because it is one-third as heavy and roughly two-thirds as conductive as copper. Applications for the metal are also growing rapidly for containers and packaging, where it is used in cans, foil, and frozen-food containers. Indeed, the metal's versatility suggests countless possible applications.
