The difference between weathering steel and ordinary steel

Weathering Steel, named after the trademarks COR-TEN Steel and Corten Steel, is a mild steel alloy developed to eliminate the need for painting and to develop a stable rust-like appearance after years of exposure to weather. Its earliest development in the United States dates back to 1933 with the United States Steel Corporation. Weathering steel is the first and oldest of the six current high-strength, low-alloy steels. Weathering steel is considered the strongest material, and its resistance to atmospheric corrosion is 4 to 8 times that of ordinary mild steel.

A unique characteristic of weathering steels is that, due to outdoor exposure, they develop a thin brown patina that differs in appearance, composition and structure from other types of rust. With constant exposure to wetting and drying, the patina will turn orange and then reddish-brown over time. After a year of exposure, bronzers can turn dark brown, especially in urban environments.

With proper maintenance, weathering steel can be placed outdoors without any paint. These properties make weathering steel an ideal material for outdoor contemporary art, primarily sculpture and architectural features. Since the 1960s, articles in professional journals have promoted the special design features of weathering steel.