COR-TEN® is a special steel alloy that has a weathered, rusty-orange look. The material, also referred to as corten or CorTen, was developed to eliminate the need for painting the metal. Cor-Ten forms a stable rust-like appearance after being exposed several years to weather.
U.S. Steel owns the trademark on Cor-Ten. This steel alloy is encouraged to rust – and form a dark brown oxidation. This rust forms a protective coating over the surface that slows further corrosion.