A weathering steel that has superior corrosion resistance over regular carbon steel because of a protective oxide film on the metal's surface. Its 50,000 minimum yield strength allows for cost reduction because lighter sections can be designed and built into structures; it is generally meant to be used in unpainted applications where a reduction in maintenance costs, such as painting, are desired. Cor-Ten is a brand name for corrosion resistant products that were developed by United States Steel; Cor-Ten has subsequently been licensed to be produced by other steel manufacturers.

Source: Art & Architecture Thesaurus

http://vocab.getty.edu/page/aat/300178799