Aluminum The Material of choice Aluminum: Aluminium is a soft and lightweight metal with a dull silver-gray appearance. Aluminium is about one-third as dense as steel or copper is malleable ductile, and easily machined and cast; and has excellent corrosion resistance and durability due to the protective oxide layer. It is also nonmagnetic and nonsparking and is the second most malleable metal (most being gold) and the sixth most ductile. Whether measured in terms of quantity or value, the use of aluminium exceeds that of any other metal except iron and it is important in virtually all segments of the world economy. Aluminium alloys form vital components of aircrafts and rockets as a result of their high strength to weight ratio. Aluminium was selected as the material to be used for the apex of the Washington Monument, at a time when one ounce cost twice the daily wages of a labourer. Aluminium was, when it was first discovered, extremely difficult to separate from the rocks it was part of.