Originally Posted by euro2fast4u
Rust needs 3 things, air, water, and steel. When you add salt you increase the flow of electrons that increase the speed of the deterioration of the metal. So how do you prevent that. Wash the salt off regularly, dry the bottom of your car, because you cant remove air
, and then inspect monthly that none of your undercoating has been scratched off or chipped. As long as the under coating is intact and 99% of the time that's the issue. You wont have to worry about rust.
Correction; oxygen (air), "electrolyte" (aka, water or soil or anything conductive) and "exposed/bare" steel.
Cars don't rot in southern wet climates like they do in snow/salty ones. That proves that water alone isn't something to worry about...though we all know a dry climate (Cali/Arizona) will see even less rust than Texas/Louisiana/etc.
Either get an undercoating (line-x, or others suggested here) to prevent bare metal exposure of the cars undercarriage or wash the car regularly to rid it of the salt. Even when you wash it, salt/water/grime/dirt/sand/etc collect in those tough to reach nooks and will cause problems, so the undercoating is really going to be your best bet if you're worried.
That said, cars corrosion resistant coatings these days goes pretty far. Unless you're planning on keeping the car a dozen years then it's not going to have problems while you own it, unless the car has had damage and the corrosion protection coating wasn't properly reapplied.
Also, I saw a post about BMWs 12 year corrosion warranty; that for full on perforation only. For it to be honored, BMW requires you to participate in an every 2 year corrosion inspection at the dealership (which you pay for)...so that usually don't help anyone.