Weathering steel, best-known under the trademark COR-TEN steel and sometimes written without the hyphen as "Corten steel", is a group of steel alloys which were developed to eliminate the need for painting, and form a stable rust-like appearance if exposed to the weather for several years.
The corten steel forms a self-protective oxide layer.
The anticorrosive properties of weather-resistant steel are based on the protective oxide layer, called patina which forms on the surface of the steel.
At first, the patina is a reddish brown color, but with time takes on a darker hue. In industrial environments, the patina forms more quickly and is darker in color than in rural areas. In marine environments, the formation of the protective patina may be slower due to chloride exposure.
Atech offers corten says: "A", that is to say, it is less porous over time and therefore more qualitative. Then, according to your desires different finishes are available: unrusted, sanded, activated, stabilizated or varnish. The unrusted corten in its basic state has no rust. If your wish to obtain a uniform color over the time, it'll be necessary to choose sanded corten steel. Then, if you want the product to be already brown at the delivery, it ll have to be activated, the finish will be sanded & activated. If, on the other hand, you do not want it to change once installed, it will have to be stabilizated. Finally, for optimum quality moreover if you wish to seat on it, we recommend to varnish it.
Atech activates the maturation of corten steel, using a system of natural oxidation through weathering, thus favoring non-invasive techniques for the environment. This natural system, gives corten steel a particular non-uniform aspect and different shades of colour. Particularly, the nuances of colour typical of corten steel are more visible in weld areas, since the formation of the patina on these points is slower.