Salt is definitely a No-Go for the reason you mentioned : corrosion.
Mind you at some Air Force Base in the Gulf region, where some pilots perform very low flights, their go through a wash bay after landing (the aircraft I mean, not the pilot alone).
This includes a line of nozzles installed in the pavement and that spit upwards to rinse the belly.
So no salt please. It's no healthy.
H.A.