Aluminum is the most prominent material in the Earth's crust. It is cheap, easy to refine and easy to handle, making it ideal for large-scale applications such as that in the beverage industry. Aluminum cans can be produced as quickly as 2,400 cans per minute. The production of the aluminum alloy used for cans is carefully controlled in an effort to reduce costs by making the aluminum stronger and more resistant to corrosion.
The main material in aluminum cans is, of course, aluminum. Aluminum is smelted out of bauxite ore. Much of the aluminum used in the United States is smelted from ore imported from Guinea and Jamaica. Aluminum is lightweight and soft, with about 1/3 the density and strength of steel. It is malleable and ductile, making it ideal for casting and drawing.
Small amounts (about 1 percent by weight) of manganese in aluminum cans helps prevent them from corroding. The manganese forms grains that absorb impurities. Manganese is hard and brittle. It has many oxidization states, ranging from minus-3 to plus-7, with the most stable being plus-2.
Present in about the same amount as manganese, magnesium strengthens the alloy used to make aluminum cans. It also makes the alloy more ductile, allowing it to stretch easily. This allows can producers to use less aluminum per can, and save money. Magnesium is extremely abundant, rating as the eighth-most abundant material on Earth and ninth-most abundant in the universe. Like manganese, magnesium is most stable in the plus-2 oxidation state. It is strong, but lighter than aluminum. When exposed to oxygen, a thin layer of silvery oxide forms and protects the rest of the magnesium, allowing it to be stored in standard conditions.
According to the Material Safety Data Sheet for aluminum alloy 3004-H19, an alloy typically used for aluminum cans, there are small amounts of iron, copper, silicon and zinc present, as well as trace amounts of other metals. Each of these other materials are present in concentrations of less than 1 percent. Aluminum alloy 3104-H19, another aluminum alloy commonly used for cans, contains titanium, gallium and vanadium in addition to the materials in alloy 3004-H19. These other materials are present in an ongoing effort to reduce the overall cost of aluminum alloys, by making them stronger and lighter. Even a minor reduction will save large amounts of money during large-scale production.
- Photo Credit Aluminum cans on end image by Jeffrey Studio from Fotolia.com
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