Black pipe, looks black from appearance. The dark color comes from the iron-oxide formed on its surface during manufacturing. Black steel pipe refers to ordinary iron pipe and are mainly used for gas lines, it is also used to connect appliances to their supply lines. It is the pipe that is used by businesses and residential homes to convey their supply of natural or propane gas.
Black steel pipe is also used for fire sprinkler systems because of its strong resistance to heat. It is usually joined by welding or by using mechanical couplings. It can even be used instead of galvanized pipe in projects other than carrying water for drinking.
Black iron pipe is actually made of a low-grade "mild steel" compound. This gives it much better corrosion resistance than traditional cast iron piping. There are few standards that all black iron pipes adhere to. However, they are all made to handle natural and propane gas, which usually stay below 60psi. The standards that black iron pipe must conform to guarantee a pressure rating of at least 150psi, if installed properly.
