If the rust is very thin you might try one part vinegar to three parts water, scrub vigorously with a green scotchbrite pads then rinse. This will neutralize the rust.
There is a you tube video called DIY AUTO SCHOOL that explains it.
I used this method on a inner wheelwell cover and it didn't rust for over a year but I kept the part inside the garage. Primed and painted the part and it still looks good years later. ETA: PPG metal prep does the same thing. I stripped the part to bare metal though. Just a suggestion.