Corten steel is an alloy steel. After several years of outdoor exposure, a relatively dense rust layer can be formed on the surface, so it does not need to be painted for protection. The most well-known name of weathering steel is "cor-ten", which is the abbreviation of "corrosion resistance" and "tensile strength", so it is often called "Corten steel" in English. Unlike stainless steel, which can be completely rust-free, weathering steel only oxidizes on the surface and does not penetrate into the interior, so it has high anti-corrosion properties.
Corten steel is considered a”living”material due to its unipue maturation/oxidation process. Shade and tone will change over time, depending on the shape of the object, where it is installed, and the weathering cycle the product goes through. The stable period from oxidation to maturity is generally 12-18 months. The local rust effect does not penetrate the material, so that the steel naturally forms a protective layer to avoid corrosion.
Corten steel will not rust. Due to its chemical composition, it exhibits higher resistance to atmospheric corrosion than mild steel. The surface of the steel will rust, forming a protective layer that we call "patina."
The corrosion inhibition effect of verdigris is produced by the specific distribution and concentration of its alloying elements. This protective layer is maintained as the patina continues to develop and regenerate when exposed to weather. So it can be used for a long time without being easily damaged.