Carbon steel pipe and black steel pipe are often used interchangeably, but there are some key differences between the two. Composition: Carbon Steel Pipe is made up of carbon as the main alloying element, along with other elements such as manganese, silicon, and sometimes copper. This composition gives carbon steel pipe its strength and durability. On the other hand, black steel pipe is a type of carbon steel pipe that has not undergone any additional surface treatment or coating. Surface Finish: The most apparent difference between carbon steel pipe and black steel pipe is the surface finish. Carbon steel pipe has a dark, iron oxide coating called mill scale, which forms during the manufacturing process. This mill scale gives carbon steel pipe its black appearance. In contrast, black steel pipe has a plain, uncoated surface. Corrosion Resistance: Carbon steel pipe is susceptible to corrosion due to its iron content. However, the mill scale coating on carbon steel pipe provides some level of protection against corrosion, especially in indoor or dry environments. On the other hand, black steel pipe is more prone to corrosion since it lacks any protective coating. Therefore, black steel pipe is not recommended for use in areas exposed to moisture or corrosive elements.