Clean the pipe thoroughly to remove grease, dirt, grime and salt deposits. Use a heavy-duty cleaner and rags to clean the pipe. Then clean it again with mineral spirits and a rag. This removes remaining grease left on the pipe or residue from the cleaner.
Rough sand the steel pipe if it has a sheeny surface that may decrease adhesion. This is true of stainless steel or chrome steel pipe. Lightly rough the surface with metal abrasive sandpaper -- 200 grit or less. Wipe away all residue from sanding with a clean towel.
Apply a primer to the steel pipe. Use metal-grade primer or automotive paint. Spray the primer onto the pipe and allow it to dry as directed in the instructions. Take care that if you are using a metal spray-paint system designed specifically for steel, you may not need a primer. Consult your paint application instructions for further information.
Apply the final coat of paint to the steel pipes as directed by the manufacturer instructions. Usually, this involves spraying the steel pipes with a coat of paint and then layering on a second coat before the paint of the first coat completely dries. That is called a wet application.