Iron corrosion, also known as RUST, is a chemical process that occurs when iron is exposed to oxygen and moisture. RUST is an oxidation reaction that causes the iron to corrode and form a reddish-brown coating on the surface of the metal. RUST can weaken the structural integrity of the metal and cause it to become brittle and eventually break down. RUST can also cause discoloration and staining of the metal, making it less attractive.