Start with a couple of pre-emptive strikes.
- Get the car waxed at the end of autumn, before the first snowfall.
- Buy a set of heavy rubber floor mats.
Time to go into full rust-fighting mode!
- Keep the floors clean. Snow on your shoes melts into salty water that can seep into the carpets and cause the floorboards to rust. Install those heavy rubber floor mats you bought. When you get into the car, kick your feet against the door sill to knock off any extra snow.
- After driving, kick off any snow and slush stuck to the bodywork just behind the wheels.
- When the temperature is below freezing, do not wash your car. The ice and snow will hold the salt in suspension and keep it from doing any major damage.
- As soon as the temp climbs above freezing, take the car to a car wash that has an underbody spray. Be sure the car wash uses fresh and not recycled water, otherwise you're just having salt from other cars sprayed onto yours. If the temperature stays up, wash the car weekly.
- Park outside. A warm garage melts the snow and ice stuck to your car and allows the embedded salt to start its destructive work on your car's body. (If cold-weather starting is a problem, buy and install an engine block heater and plug the car in at night.)
When the snow is gone for good, check your car for signs of rust. Remember, once rust starts, it only gets worse, so consider having a competent body shop repair any rust spots. Enjoy the summer, and get ready to do battle again next year!