Corrosion Science rusted bridge girders Corrosion is a natural phenomenon, a chemical process rooted in science. Metals have a tendency after production and shaping to revert back to their lower energy, more natural state of ore (e.g. iron ore). The tendency is known as the Law of Entropy. It is very rare to find metals in their pure state naturally, more commonly, they are combined with other elements to form ores. In the steel industry, great efforts are expended to turn naturally occurring iron ore into steel. Corrosion is the reverse process of metallurgy. In other words, the energy used to transform ore into a metal is reversed as the metal is exposed to oxygen and water. As the metal is exposed to these elements, the corrosion process begins – oxides are formed on the steel surface and in some cases combine with sulfides and carbonates.