Think about it; how many rusty Glocks have you seen?
I had a 10mm Glock that I used for dispatching halibut. After a season on the boat, providing Glockoma treatments and periodically getting splashed with saltwater, in the process, it did rust. It still functioned like a Glock, of course, but it definitely got ugly.
In the end, I learned that the only thing saltwater won't screw up is saltwater.