Stainless steel 1.4408 suits corrosive, hygienic or high-temperature media (chemical, pharmaceutical, food). Carbon steel 1.0460 is the more economical option for neutral media at high pressures (power plants, district heating, steam condensate). Ductile iron GGG40 is the standard for water, gas and building services — with the option of DVGW certification (KH121). For chloride-bearing media or seawater, duplex stainless steel 1.4470 is recommended.