It is very common to see black pipe used for your natural gas line and sprinkler system lines. Since black pipe has no protective coating, it may rust easily in wet or humid environments. To stop the pipe from rusting or corroding on the outside, you should provide a layer of protection on the outside of the pipe.

Will black steel rust?

The alloyed combination makes the steel both more durable and more rust-resistant. ... Black steel is even less expensive than galvanized steel because it isn't coated or alloyed. Instead, it becomes covered in iron oxide (rust) during the manufacturing process.

How do you stop black iron from rusting?