S355JOWP Weathering Corten Steel is high-strength self-passivizing, containing copper, chromium and phosphorus, characterized by high corrosion resistance (cor-rosion) and high yield tensile (ten-sile) strength; these alloys have the property of self-protection through the formation of a superficial coating that prevents progressive spread of corrosion

Weathering steel, best-known under the trademark COR-TEN steel and sometimes written without the hyphen as "Corten steel", is a group of steel alloys which were developed to eliminate the need for painting, and form a stable rust-like appearance if exposed to the weather for several years.