It is the winter hitch-hiker, none of us wants on our cars: Road salt. But how much damage does salt really do? And how often should we get our car washed?

"I believe, the more you can wash the car, the more you can keep some of that salt off, it's going to benefit it in the long run," said Matt Feehan, President of American Auto Body in Brooklyn Park.

And long-run is the key. Salt doesn't generally show up as rust in short order. It takes time, and salt doesn't cause rust in paint, it rusts metal.

"It has to go through the coating, through the e-coating, the primer, and into the bare metal to have an effect," said Feehan.

So it's not easy for salt to cause damage, especially considering the dramatic improvements in paints and primers.

"The corrosion-resistant coatings are better and the manufacturers are more complete in the painting processes," explained Feehan. "All of these components are heavily built, so it's largely a cosmetic issue."

However, according to Feehan, salt can cause rust to build up on hidden parts of your car, and slowly eat away at the metal. It can take years for the rust to manifest itself on the car's exterior.

Frequent washing gets to those hidden spots, according to Feehan, who washes his car once a week.

"It's that middle temperature that's from 5 degrees to 35 degrees that really makes a mess. If you know we're going to go into a deep arctic plunge, so to speak, at that point get your car washed before that," he suggested.

If you park your car in a warm garage, you are at higher risk that salt is going to damage your car. Rust forms when moisture and oxygen combine on metal, and salt accelerates that process because it corrodes.

If you park in a warm garage, you melt the ice that forms on your car during the winter. That melting provides moisture, which hits the salt, which can cause rust.

"The idea of a car coming in and out of a warm environment is great for the driver, it's great on motor and transmission, however on the body it is more difficult," said Feehan.

He suggests waxing your car in the fall, which provides a layer of protection, making it easier to remove the salt, which inevitably will build up on your car in the winter.

Preventing Rust from Road Salt

Plan Ahead

The best time to prevent salt damage to your vehicle is before the first snowflake falls.

• In late autumn, thoroughly wash every inch of your vehicle, including the underside.
• Apply a meticulous coat of wax, followed by a wax sealant to help keep the wax adhered to the vehicle's paint.

Keep a Clean Vehicle

Keeping your vehicle as clean as possible during the winter will go a long way to cut down the damage done by salt and sand.

• Take your vehicle to the car wash as often as possible. Many car washes offer undercarriage cleaning as well as traditional car washing.
• Have your car re-waxed and sealed when you have it washed.
• Check out a mobile automobile detailer who can come to your workplace and do several vehicles at once.

Beach Buggies Beware

If you live near the ocean - even if it has never, ever snowed in your area - your vehicles may still be under a slower attack by salt. The overspray and salt in the air near the beaches can and do cause their own rust and corrosion problems. While not nearly as concentrated as the salt used on winter roads, it is important to keep your seaside sedan washed, waxed and inspected regularly for signs of salt damage. The biggest damage areas on beach-dwelling vehicles tend to be the hood, top, and rear deck of the car. Spray settles and dries, leaving a salt coating. Vinyl tops are especially susceptible to deterioration from exposure to salt and sun. Once the vinyl begins to break down, salt spray can accumulate underneath, and may go undetected until it has caused serious damage. Give your beach mobile a good washing at least once a month.