What is the black pipe?

Black steel pipe is made of steel that had not been galvanized, Its name comes from the scaly, dark-colored iron oxide coating on its surface, It's used in applications that don't require galvanized steel.

What is carbon steel pipe?

Steel whose characteristics are determined by the amount of carbon it contains. And steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, niobium, molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 percent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60.

Most the steel produced in the world falls into the category of carbon steel.

Difference between black pipes and carbon pipes

In general "black" steel pipe and carbon steel pipe have about the same procedures for welding. That is if you are talking about general welding and not for some specific application like very cold temperatures. Black steel pipe is not really a specification but rather a generic term used primarily by plumbers to distinguish regular steel pipe from galvanized steel pipe. Most black steel pipe has a composition similar to ASTM A-53 pipe. The difference between A-53 and common steel pipe like A-106 are so close that some pipe is actually marked to meet both specifications. Black pipe and A 53 can be seamless or welded seam while A 106 is seamless.