Black pipe is plain steel pipe without any protective coatings. Black pipe is used for a variety of applications around the home. 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. The easiest method is painting it.
Clean the surface of the pipe to remove any rust, loose paint or oils. Scrub the areas with rust or loose paint with a wire brush and wipe down the oily areas with a cleaning agent such as acetone.
Apply a thin layer of rust-inhibitive primer. Spray cans allow for quick and easy applications–especially in hard-to-reach crevices between the black pipe and the fittings. Allow the primer to dry for the recommended time and then re-coat with another layer of primer.
Spray on your first layer of topcoat. Move the spray from side to side to ensure even coverage. Allow to fully dry and then apply a second coat.
Touch up the paint as necessary to prevent larger repairs down the road. If the paint becomes damaged, rust can develop at the damaged site, which may possibly begin to affect the paint around it, leading to cracking, peeling and other damage. If damage is spotted, immediately re-prime and re-paint the affected area.