Corten is a type of steel that naturally weathers and develops a layer of attractive rust with a protective layer. It is really a paradox, as although it is rusted, to a degree, the surface actually has a layer that protects against further corrosion. In other words, the steel is allowed to rust in order to form the protective coating. This protective layer develops due to the elements that are active in the alloys of the steel. It regenerates continuously when subjected to the influence of water and oxygen.