COR-TEN has served as weathering steel (atmospheric corrosion- resistant steel). Corten steel plate has successfully overcome rust, steel's most weakest. When exposed to the atmosphere without painting, corten steel begins to rust in the same way as ordinary steel. BUT soon the alloying elements in COR-TEN cause a protective surface layer of the fine-textured rust to form, thereby suppressing corrosion rate. Since its development in 1993, the COR-TEN has been used in every field where steel applied, such as bridges, railway vehicle and buildings. At present, COR-TEN are attracting attention as being suited for resources and environmental concerns as well as reducing life-cycle costs.