Information on Recycling Aluminum
Collection & processing
Aluminum cans are more widely recycled than any other consumer container. Some people take them to recycling
centers that pay cash, while others donate them to nonprofit groups that sell cans to raise funds.
Recycling centers and small businesses that buy back aluminum cans must rely on the public to assure that
cans arrive free of contaminants. The larger companies that buy baled aluminum from recycling centers will
reject contaminated loads, or even cease to do business with centers that bring in contaminated loads. Neglect
on our part can put recycling centers out of business, or keep large amounts of aluminum from being recycled
because it is too dirty or contains too much water.
Most aluminum cans are used to produce sheet aluminum for making new cans. The sheet aluminum plant receives bales
of used cans. These are melted down, and lacquered labels burn off in the process.
Can tops are made of an alloy containing a higher ratio of magnesium than the alloy used for the body of the
can. As a result, the molten aluminum derived from complete cans has too little magnesium for new tops, and too
much for new bodies. New aluminum or scrap low in magnesium is therefore added to the batch. This brings the level
of magnesium down until it is suitable. The resulting aluminum is rolled into sheets that are used by can makers
to fabricate new can bodies.
Sheet aluminum is thicker than the wall of a finished can. During the process of making a can, the aluminum is
stretched much thinner. The process begins by punching circular sections out of the sheet. The resulting aluminum disks
are pressed into cup shape. The walls of these cups are elongated by an "ironing" process: round, heated machinery
spreads the aluminum upwards much as a rolling pin will expand the area of a pie crust.
The thickness of a finished can is not uniform, however. The bottom and the upper rim are thicker. When the can
is of sufficient height, the top is trimmed level and clean. A concave dome is pressed into the bottom, and the upper rim is
angled inwards then partially flanged outwards. A label is lacquered onto the outside surface and the inside is coated
to prevent corrosion and preserve taste.
Tops are also made from sheet aluminum, though its thickness and the alloy are slightly different from the sheet used for
can bodies. Also, the anti-corrosive coating will already be on this sheet when disks are punched out. This is possible
because tops retain their original thickness instead of being pressed wider and thinner. The edges are curled where the
tops will attach to the flanged upper rim of the can, and a button is pressed into its center. The button serves as an
attachment for the tab, which will later be used to pop open the can. The edges of that potential opening are pressed very
thin before the tab is attached.
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