The Rust Process

Rust is the name for the common compound Iron Oxide ( Fe2O3 ). Iron Oxide combines very readily with oxygen. Corrosion or Rust is an electrochemical process involving an anode (a metal that readily gives up electrons) and an electrolyte (a liquid that helps electrons move). When a piece of metal corrodes, the electrolyte helps provide oxygen to the anode. As oxygen combines with the metal, electrons are liberated.


For iron to become iron oxide, three things are required: iron, water and oxygen. When a drop of water hits an iron object, two things begin to happen almost immediately. First, the water, a good electrolyte, combines with carbon dioxide in the air to form a weak carbonic acid, an even better electrolyte. As the acid is formed the iron begins to slowly dissolve, some of the water will begin to break down into its component pieces -- hydrogen and oxygen. The free oxygen and dissolved iron bond into iron oxide, in the process freeing electrons. In other words; when metal is exposed by a scratch to water and air, it gives up electrons which changes the metal composition and allows Rust to form.