The material used for CorTen is an alloy of iron, copper, phosphorus, silicon, nickel and chrome. Due to the effective protective layer, CorTen steel allows you to make savings by eliminating extra surface treatment processes such as galvanising.
CorTen steel owes its good weathering resistance to a tight oxide skin. This layer, the patina, protects the core material against (further) degradation. This protective layer forms naturally through oxidisation when the material is exposed to the elements. In other words ‘normal’ atmospheric conditions.
Only then does the patina layer form on the surface. This process can take months, or even years, depending on local conditions.
Thanks to the patina on the surface, CorTen steel is capable of lasting for decades in outdoor applications. However, the structural design must take a number of important points into consideration. For example, blind holes where water can accumulate should be avoided.