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.
Underbody cleaning is the act of cleaning the underside of the car to remove any dirt and restore the looks as when the car was new. This is a tedious and labor intensive job, but good cleaning products and tools can help to make it easier.