Weathering or rusting steel, often known by the trademark name COR-TEN® is a group of steel alloys developed to form a stable rust-like appearance if exposed to the weather for several years. No other finish is needed for weathering steel, because the steel is allowed to rust and that rust forms a protective coating that slows the rate of future corrosion. This gives weathering steel increased resistance to atmospheric corrosion compared to other steels.

The steel arrives unrusted and will rust over time with natural exposure to the weather. The rust run off will stain surrounding areas, so it’s not recommended for use on light coloured areas such as balconies or woodwork or light pavements.