Cathodic protection is real, but I don't think it would work very well on a car. A ship's hull benefits from it becauze it's one big hull of a piece of steel.

I get the "Rustchek" every year. I, and many people I know, swear by it.

Oh... I live about 20km from salt water.... New Brunswick, Canada. So, we also get a LOT of road salt and freeze-thaw.