Can aluminium rust?
Can aluminium rust? In short, no. Rust is the process whereby ferric metals (iron and steel) oxidize, or come into contact with water and oxygen. As aluminium is not a ferric metal, it won't rust but corrodes. Rust refers only to iron and steel corrosion. Aluminium oxidisation Oxidisation results in a skin of aluminium oxide coating the metal, which in turn protects it from further oxidation. For this reason, an aluminium can will take an incredible 10,000 years to disintegrate. Aluminium oxide is white and coats aluminium making it less bright. When aluminium starts to dull a little, it has oxidised. Aluminium oxide is impermeable and adheres strongly to the parent metal. If damaged mechanically, aluminium’s oxide layer repairs itself immediately. The most common types of aluminium corrosion: • Pitting: Pitting is by far the most common type of corrosion in aluminium. It occurs only in the presence of an electrolyte (either moisture or water) containing dissolved salts, usually chlorides. Pitting is primarily an aesthetic problem that doesn’t affect strength. • Galvanic corrosion: Where there is both metallic contact and an electrolytic bridge between different metals galvanic corrosion occurs. • Crevice corrosion: Crevice corrosion can occur in narrow, liquid-filled crevices. The chance of this kind of corrosion occurring in extruded profiles is small. However, significant crevice corrosion can occur in marine atmospheres and the exteriors of vehicles.