I concur John, I have seen AFS filters packed with salt. The seem to do a pretty good job stopping it.
One thing I learned from my insulator washing experiences. There is way more airborne salt the closer to the equator you get. I assume its just a result of more evaporation. Power companies on the gulf and southern California coasts have to wash salt from their power lines annually. In the northwest and north east. I've never heard of it.