Corten steel is almost pure carbon steel, but has been weatherproofed to create a protective layer against the weather. The surface is initially reddish brown (colour is similar to rust), but over time the colour becomes a little darker. When used as intended, cor-ten steel is expressive, maintenance-free and remains in good condition for a long time. The products made of corten steel do not need to be stored indoors or covered in winter, as the stainless steel can withstand all weather conditions.