Rusty Top Pool Rails

So I have a 24ft round in Pittsburgh. Several of the steel top rails keep developing surface rust. I've popped the affected rails off many times to sand, treat the rust, and repaint, only to have the rust reappear the next year.

Are there places to take the rails a few at a time to have them thoroughly sand blasted and the powder coated?

Or is there another solution I'm not aware of?