Even US Steel hasn’t recommended corten steel for “architectural application[s], such as roofing and siding” for the past two decades. The reasons given are that abrasion from weather and acid rain cause the oxide skin on the material to reform, which causes the material itself to eventually become perforated. Can we justify using materials that we know may need to be replaced in the near future?
Instead, US Steel offers an alternative product for architectural use: COR-TEN AZP. This product has improved solar reflectivity (which is better for roofing), no unsightly staining from water runoff, and a high recycled content and recyclability. While that may sound positive, up to two-thirds of steel production already involves recycling, and large amounts of carbon dioxide are emitted from burning coal and coke as part of the process. This can be hazardous to human health — and it can cause environmental problems.
Steel begins life as iron ore, and it is usually obtained through open-cast mining. This method of extracting resources can cause many environmental issues. When rocks are broken open, biodiversity is threatened, erosion and sinkholes occur, and harmful and radioactive substances are released into the environment.
Later in the steel production process, sulphur oxides, nitrogen oxides, and carbon monoxide are all released into the atmosphere as a result of smelting. The iron and steel industry is the largest global source of CO2 emissions and the second-largest industrial consumer of energy. A 2012 report shows that that this energy use and its resulting emission of greenhouse gasses could vastly be reduced if the industry instead relied on renewable electricity sources. This is unlikely to happen in the near future, however, because of the high cost of implementing the new technology.