Black Iron Pipe vs Steel Pipe
There are serious differences between black iron pipe and steel pipe. The iron is ductile and malleable and a black iron pipe is made from grades of the metal. It is used in seamless or wrought wielded. You can use malleable iron for supply of water. However, this is not possible for steel as areas are bound to shed from inside.
The main difference between the two products is in their original properties. While iron contains high carbon content and is austenitic with cementite, steel, on the other hand is ferritic. Black iron pipe is, by all means, a pipe painted in black. The term is commonly used in the Unites States.
However, in the real sense of example, many people mistake black iron pipe as a steel pipe. Hence you need to specify as to what you want. The difference between is immediately understood in presence of water. The black pipe was called as black iron pipe recently. There are, as mentioned earlier, differences between back iron and steel pipes. You can bend steel but not iron. Both, the black iron and the steel pipe have a significant self life.