Weathering steel

Rust on Cor-Ten — Texture of a sheet of Cor-Ten after being exposed to the elements for 5 years. The rust can form unevenly based on the composition of the metal.

Weathering steel, often referred to by the genericised 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 after several years' exposure to weather.

U.S. Steel (USS) holds the registered trademark on the name COR-TEN.^[1] The name COR-TEN refers to the two distinguishing properties of this type of steel: corrosion resistance and tensile strength.^[2] Although USS sold its discrete plate business to International Steel Group (now ArcelorMittal) in 2003,^[3] it still sells COR-TEN branded material in strip-mill plate and sheet forms.

The original COR-TEN received the standard designation A242 (COR-TEN A) from the ASTM International standards group. Newer ASTM grades are A588 (COR-TEN B) and A606 for thin sheet. All alloys are in common production and use.

The surface oxidation of weathering steel takes six months, but surface treatments can accelerate the oxidation of weathering steel to as little as one hour.^[4]

^ "Trademarks and Ownership". USS. Retrieved 13 June 2017.
^ "Weathering Steel: A Guide to Corten and the A/B Equivalents, Origins & Standards". AZoM.com. 4 July 2016.
^ Plate Products, 31 October 2003, archived from the original on 28 December 2007, retrieved 13 January 2010
^ "Corten+ US". Corten+ | Rust accelerator. Retrieved 20 November 2021. The Corten+ treatment products form a rust in one hour

[1] "Trademarks and Ownership". USS. Retrieved 13 June 2017.

[2] "Weathering Steel: A Guide to Corten and the A/B Equivalents, Origins & Standards". AZoM.com. 4 July 2016.

[3] Plate Products, 31 October 2003, archived from the original on 28 December 2007, retrieved 13 January 2010

[4] "Corten+ US". Corten+ | Rust accelerator. Retrieved 20 November 2021. The Corten+ treatment products form a rust in one hour

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