Carbon Steel vs Black Steel

Carbon steel is susceptible to corrosion. Blackening is a process to create a tenacious oxide coating that provides some corrosion resistance. 

Black steel is made of steel that has 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.

There are different classes of carbon steel. They are categorized by the percentage of carbon that is mixed with the base element, iron.
Classes of carbon steel Carbon content %
Ultra-high carbon steel 1.00 – 2.00
High carbon steel 0.60 – 0.99
Medium carbon steel 0.30 – 0.59
Low carbon steel 0.16 – 0.29
Mild carbon steel 0.05 – 0.15

Black steel pipe is manufactured as seamless which makes it a better type for gas transportation. It can be used for fire sprinkler system since it can prevent fire better than galvanized pipe. Since it has a dark color surface that is form by iron oxide during the manufacturing process, it is called black steel pipe.

Black steel pipe's strength makes it ideal for transporting water and gas in rural and urban areas and for conduits that protect electrical wiring and for delivering high pressure steam and air. The oil and petroleum industries use black steel pipe for moving large quantities of oil through remote areas. This is beneficial, since black steel pipe requires very little maintenance. Other uses for black steel pipes include gas distribution inside and outside homes, water wells and sewage systems. Black steel pipes are never used for transporting potable water.