Corten steel is a high strength weathering steel. The word “CorTen” is the trademark name given to a weathering steel alloy material originally produced by United States Steel. CorTen Steel is no longer produced in the United States. This steel alloy falls into the category of those that were developed to reduce or eliminate the use of coats, primers or paints on the material to make it rustproof. When exposed to the environment, this steel forms an outer layer platina that protects this steel from corrosion. This is the reason why this steel is called weathering steel. CorTen steel or weathering steel is a corrosion-resistant material. When left uncoated, it forms a protective layer (platina) on the outer surface that protects this steel material from acidic environments and corrosion.