Aluminum is a silvery-white metal, and its content in the earth’s crust ranks third after oxygen and silicon. Aluminum has a low density, only 34.61% of iron and 30.33% of copper, so it is also called a light metal. Aluminum is the non-ferrous metal with the second largest output and usage in the world after steel. The density of aluminum is only 2.7103g/cm³, which is about 1/3 of the density of steel, copper or brass. Because aluminum is light, it is often used in the manufacture of land, sea and air transportation vehicles such as cars, trains, subways, ships, airplanes, rockets, and spacecraft to reduce their own weight and increase their load capacity.
