Here's the thing about rust, there is a reason it's nicknamed cancer, if you don't cut ALL of it out and patch it it's just going to spread.
'rust converters" DON"T WORK
just sanding it down the best you can and primering it works SOMETIMES, but it is rare that it won't come back
"sealer pprimer, rust inhibitor, jb weld, bondo, rustoleum, naval jelly" none of it works, you must cut 100% of it out, weld in new metal and do it right, that way you will get another 15 years out of it instead of 15 weeks.