Weathering steel forms a protective layer on the surface of the metal substrate through the alloying of Cu, P, Cr, Ni, etc., so that it has high atmospheric corrosion resistance. This type of steel has better weathering properties than weathering steel for welded structures, so it is called high weathering structural steel.

Weather resistant steels are high strength, low carbon structural steels including small amounts of alloying elements such as copper, chromium, nickel and phosphorus. As a result of these alloying elements and effects of oxygen and humidity, a protective oxide layer is formed on the surface of the steel. The oxide layer prevents the steel from corroding beneath the surface. The thick oxide layer regenerates itself in case of surface damage. The patinated brown-orange appearance of weather resistant steel is formed when the steel is exposed to various weather conditions like humidity and drought. It takes approximately 18-36 months until the protective layer is formed under normal weather conditions. Weather resistant steels are cold formable and great to weld.