Funny you should ask
Just last night I decided to do something about my crappy looking rear bumper. It's homemade from two Smittybilt step rails off a full sized pickup. Had some really ugly welds and was rusting.
I took it down to bare metal, ground down the pipe welds, hosed it off, dried it with a torch, then shot it with Rustoleum bed liner.
Here it is this morning after mounting it