Rust is an iron oxide , a usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture . Several forms of rust are distinguishable both visually and by spectroscopy , and form under different circumstances . Rust consists of hydrated iron ( III ) oxides Fe O nH O and iron ( III ) oxide - hydroxide ( FeO ( OH ) , Fe ( OH ) ) .

Question: what happens when iron reacts with oxygen and water
Answer: Rust