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 “Cor-Ten”. This steel alloy is encouraged to rust – and form dark brown oxidation. This rust forms a protective coating over the surface that slows further corrosion. Click to read more.