Rust remover/sealer?

[C&C Chevy]

Spent the last couple hours removing rust from passenger side cab to door area. The factory caulk was loose and the seam along side the door striker was rusted and pitted pretty bad. I've got most of the rust removed mechanically, but i'm worried about it creeping back from the inside.

Using a good rust remover/sealer is the only thing I can think of to prevent that. Anyone got a good rust sealer to recommend? Or any other recommendations? Thanks.