Rust on My Pool Rails

[Duvebrad]

the top rails of my above ground pool are metal. Some of them are rusty. The one under the ladder is the worst. My wife painted them last year, the rust seems to be coming back. I don't know what prep she did or what paint she used. I want to work on fixing them this summer. Whatever products I use, it will have to be brush-on. I don't want the overspray getting in the pool or on the deck. My prep will be to sand off any loose rust and then recoat. I need something that will stop the rust and then hold up to a fairly corrosive environment - chlorinated salty water. Is rustoleum going to do this or do I need something else? Can I get truck bed liner that can be colored white and rolled or brushed on? Would truck bed liner be too rough of a surface for bare feet, etc?

Thanks a lot.