of these steels, allowing them to exhibit increased resistance to atmospheric corrosion compared to other steels. This is because the steel forms a protective layer on its surface under the influence of the weather. The corrosion-retarding effect of the protective layer is produced by the particular distribution and concentration of alloying elements in it. It is not yet clear how exactly the patina formation differs from usual rusting, but it's established that drying of the wetted surface is necessary and that copper is the most important alloying element. The layer protecting the surface develops and regenerates continuously when subjected to the influence of the weather. In other words, the steel is allowed to rust in order to form the protective coating. The mechanical properties of weathering steels depend on which alloy and how thick the material is. ASTM A242 The original A242 alloy has a yield strength of and ultimate tensile strength of for light-medium rolled shapes and plates up to thick. It has yield strength of and ultimate strength of for medium weight rolled shapes and plates from thick. The thickest rolled sections and plates – from thick have yield strength of and ultimate strength of . ASTM A242 is available in Type 1 and Type 2. Both have different applications based on the thickness. Type 1 is often used in housing structures, construction industry and freight cars. The Type 2 steel, which is also called Corten B, is used primarily in urban furnishing, passenger ships or cranes. ASTM A588 A588 has a yield strength of at least , and ultimate tensile strength of for all rolled shapes and plate thicknesses up to thick. Plates from have yield strength at least and ultimate tensile strength at least , and plates from thick have yield strength at least and ultimate tensile strength at least . Uses Weathering steel is popularly used in outdoor sculptures for its distressed antique appearance. One example is the large Chicago Picasso sculpture, which stands in the plaza of the Daley Center Courthouse in Chicago, which is also constructed of weathering steel. Other examples include Barnett Newman's Broken Obelisk; several of Robert Indiana's Numbers sculptures and his original Love sculpture; numerous works by Richard Serra; the Alamo sculpture in Manhattan, NY; the Barclays Center, Brooklyn, New York; the Angel of the North, Gateshead; and Broadcasting Tower at Leeds Beckett University. It is also used in bridge