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Credit: Roger McLassus
Rust is the chemical substance formed when iron compounds corrode in the presence of oxygen and water. It is a mixture of iron oxides and hydroxides. Rusting is a common term for corrosion, and usually corrosion of Iron. Iron is found naturally in the ore haematite as iron oxide, and metallic iron tends to return to a similar state when exposed to air, (hydrogen, oxygen, nitrogen, etc.) and water. This corrosion is due to the oxidation reaction when iron metal returns to an energetically favourable state. Energy is given off when rust forms. The process of rusting can be summarized as three basic stages: The formation of iron(II) ions from the metal; the formation of hydroxide ions; and their reaction together, with the addition of oxygen, to create rust.