The only thing I have seen in a beach-front situation is the polepieces on a Stingray rust - buddy of mine has a house gig in Destin, FL, and his polepieces were totally rusted!
Now, if you work a cruise ship gig, or are on the water constantly, I have seen it eat hardware. One time when I was working at Bass Central, we got an Elrick fretless on trade that I had to remove all of the hardware from and clean all of the corrosion off of.