IMPROVED STEELS FOR ATMOSPHERIC CORROSION – CORTEN

In Europe it is the EN 10025-5 standard that deals with these construction steels whose origin dates back to a patent of the 1930s: in those years, in fact, the United States Steel Corporation (USS) patented an improved steel calling it COR-TEN, acronym of high corrosion resistance (CORrosion resistance) and high mechanical resistance (TENsile strength), its 2 main characteristics.

The high resistance to atmospheric corrosion is obtained thanks to a phenomenon similar to the passivation of stainless steels: the protective surface oxides that are formed are very resistant and have a brown color of different shades depending on the surrounding environment and the exposure time. As with stainless steels, the oxide coating reforms when removed (self-passivation). Generally, it can be assumed that in an urban or rural environment the corrosion of COR-TEN stops after a thickness reduction of about 0.5 mm, while in more aggressive environments it progresses at a much lower speed than a carbon steel.

Thanks to this feature, COR-TEN can be used without protective covers such as galvanizing or painting. If, for aesthetic reasons, painting is necessary, the ordinary maintenance of the coating is much less than in the case of normal steel. The high mechanical resistance allows the reduction of the weight of the structures and consequently of the costs with the same performance.

Today COR-TEN is mainly used for facades, bridges and street furniture, due to its characteristic of being up to 8 times more resistant to corrosion than common carbon steel.