The weathering steel, commonly referred to by the generic trademark COR-TEN steel and sometimes written without the hyphen as corten steel, is a class of steel alloys which can be used to eliminate the need for painting and form a rust-like appearance after being exposed to the elements for several years.
Corten steel, also known as weathering steel, is an alloy of steel commonly used for outdoor construction projects. Rusted steel eventually develops a rusted appearance as it is exposed to the elements.
During the 1930s, U.S. steel developed a product called Corten Steel. It was originally designed to help build railroad coal wagons. Coal wagons became a popular medium for outdoor art projects in the 1960s because of their success.