Salt is an unwelcome type of contamination on your vehicle. Salt can cause rapid corrosion and extreme dage to unprotected metals. It can also severely stain polished metals and create a matte look over the surface.
Paintwork can, in some cases, become oxidized. Making it turn matte and slightly fade color. If untreated, it can eventually cause the lacquer and/or paintwork to completely fail. It is most common on red cars, but it can happen with every color.