Corten steel
The name Cor-Ten comes from the initials of the two English terms used to file the patent in 1932: CORrosion resistance and TENsile strength.
The word “CorTen” is the trademark name given to a weathering steel alloy material originally produced by United States Steel.
CorTen is a low alloy steel with 0,2 - 0,5% di copper, 0,5 - 1,5% di chromium e 0,1 - 0,2% di phosphorus.
CORTEN thickness 5 mm R 25, Bressanone - Realized by Graepel Italiana Spa
The great success of CorTen can be attributed to its two main characteristics: mechanical strength and controlled oxidation.
This two features along with its aesthetic quality are the keys of the success of this material, which lately has become more and more appreciated by architects and designers.
Its patina prevent the progressive corrosion process in the internal part of the metal providing a smooth and resistant surface, with unique chromatic characteristics.
Weathering steel
In the presence of moisture and air, all low alloy steels have a tendency to rust, the rate of which depends on the access of oxygen, moisture and atmospheric contaminants to the metal surface. As the process progresses, the rust layer forms a barrier to the ingress of oxygen, moisture and contaminants, and the rate of rusting slows down.
The rust layers formed on most ordinary structural steels are porous and detach from the metal surface after a certain time, and the corrosion cycle commences again. Hence, the rusting rate progresses as a series of incremental curves approximating to a straight line, the slope of which depends on the aggressiveness of the environment.
The color changes during the oxidation process: from an initial orange color to a brown-reddish as the patina stabilizes. Under normal weather conditions, the oxidation process is completed in 18-36 months, with a thickness decrease of 0.05 mm.
Research has shown repeated wet-dry cycling is essential to form the optimum dense and adherent rust layer, with rainwater washing the steel surface well, accumulated moisture draining easily, and a fast drying action.
In industrial areas, the patina appears in a shorter time and with a darker tone; this is due to the pollutant agents and the lower presence of oxygen in comparison with the rural areas.
Cor-Ten effect
In order to create the reddish patina, CorTen is mainly used for outdoor structures.
Since today this particular steel is widely appreciated and used there are many imitations of this material that can be applied indoor. This imitations are improperly called CorTen.
One of the most used techniques to obtain simil corten effect is painting. This paint can reproduce the rusty effect. The advantage of simil CorTen painting is the uniformity of the surface that doesn't change over time.
