Corten Steel Decorative panel. These panels help add structure to your outdoor space. They can be used to create a private and intimate area in an exposed area of your garden. Made from Corten Steel category A type S355JOWP giving a very strong, wear-resistant and durable product. Corten Steel, also known as weather resistant steel, is a steel alloy made of iron which has copper, silicon, nickel and chromium added. As soon as Corten Steel is exposed to the elements it will naturally weather and develop a protective layer of rust. This natural fixed coating of rust provides protection against further corrosion. Characteristic of Corten Steel is the orange brown rust colour and its longevity.