Core-Ten steel

Developed in 1920, Cor-ten is the registered trademark name of a group of weathering steels produced by US Steel. Cor-ten steels are corrosion resistant, low-alloy, low carbon steels that form a protective coating of rust (hydrated iron oxide) when exposed to most natural environments. Frequently used in an unpainted condition, since the 1950s the steels have been used by many sculptors.