Black pipe

Black pipe is a common type of steel pipe.

Cold rolled steel becomes blackened when heated to annealing temperature, as the surface color darkens due to contact with air at high temperatures. This is known as black annealed steel. Its surface has not been polished, hence the black color. The physical properties become softer, making it easier for further welding into steel pipes. Common hardness is 57HRB, and it can be annealed to different hardness levels as needed.