Weathering steel is a specialty steel which generates patina (rust layer) while in contact with the atmosphere for a specific time. Moreover, to produce a patina layer on weathering steel, it requires alternate wet and dry cycles. Also, the generation of the layer depends on the area, climatic conditions, and other aspects. Thus, it is manufactured generally in the unpainted form which has a life span of 120 years. Unpainted weathering steel is used commonly in places where the steel is not always in contact with water such as railway bridges, containers, sculptures, and others. Some manufacturers offer pre-weathered weathering steel which is again a category of unpainted weathering steel.
Based on end-use industry, the building & construction industry led the weathering steel market in 2018, owing to specific application areas, increasing investments, and product innovation in weathering steel. Additionally, emerging nations such as China, and India are undertaking infrastructure development, which is expected to create the demand for weathering steel in the near future. Moreover, the ability of weathering steel to exhibit aesthetic and antique appeal over a period of time makes it an attractive choice for art and architecture.
The North America region led the weathering steel market in 2018, which is expected to grow at a high rate during the forecast period, owing to the increasing demand for weathering steel from the U.S., Canada, and Mexico. High demand from end-use industries such as aerospace & defense, medical & dental, automotive, electronics, and others are driving the growth of weathering steel markets in these countries.
Rust is a phenomenon that most engineers seek to avoid, but is actually desirable in weathering steel. Also known as Corten steel, weathering steel is characterized by what the American Institute of Steel Construction (AISC) describes as “useful corrosion,” in which naturally occurring rust not only lengthens the lifecycle of a weathering steel structure, but also saves the time and money associated with painting and maintenance. Rust on weathering steel sheets is not a sign of deterioration as with corrosive steel sheets; in fact, it is just the opposite.
Corten, which was trademarked by the United States Steel Corporation (USS), is the well-known brand name of weathering steel. Corten originally received the ASTM standard designation of A242, but is now recognized by the newer ASTM grade for steel sheets and coils, A606. Weathering steel was specifically developed with small amounts of copper, phosphorus, chromium, nickel and silicon. These materials allow Corten steel sheets to form a layer of rust when exposed to weather, excluding the need for paint.