Aluminium is a chemical element. The symbol for aluminium is Al, and its atomic number is 13. Aluminium is the most abundant metal. Many things are made of aluminum. Much of it is used in overhead power lines. It is also widely used in window frames and aircraft bodies. It is found at home as saucepans, soft drink cans, and cooking foil. Aluminium is also used to coat car headlamps and compact discs. Pure aluminium is very soft, so a harder metal is almost always added. The harder metal is usually copper. Copper/aluminium alloys are to make ships, because the aluminium prevents corrosion, and the copper prevents barnacles. Aluminium compounds are used in deodorants, water processing plants, food additives, and antacids.