I've got a preventive product that will help immensely!
Fluid Film
I've used this on 1980's production Desert Eagle pistols that have been left to rot and if it's used properly it will kill the rust, bubbling like hydrogen peroxide. Depending on how bad the rust is, it may require a buffing wheel to help pull it out of the finish with the FF.
BTW, Fluid Film CANNOT help the rusting issues we've been seeing lately with the Ruger LCP. After the tornado hit Joplin, Mo I had a dozen people with Ruger LCP's ask me to clean up their rusted pistols. They were completely ruined and could only be helped by refinishing or replacing the entire pistol. One of those was a LEO who had his in an ankle holster the entire time, the humidity radiating off the wet ground surfaces ruined his LCP, so much so that I could tell what parts were exposed and what parts contacted clothing...worse still was that it wouldn't cycle properly.