Unlike steel, aluminium doesn’t rust. When steel is cut, rust begins to form instantly; if left unchecked, rust will spread and become flakey, and ultimately the steel object will fail. Not so with aluminium. When aluminium is cut, the exposed surface reacts with the oxygen in the air to form an extremely thin layer of oxide. This oxidised layer then serves to protect the base material underneath and improves the aluminium’s resistance to corrosion in harsh environments. This naturally- occurring layer is self-repairing if damaged.