Your car hates winter. Not because of the cold, the snow, the traffic or the constant digging and shoveling; that’s why you hate winter. No, your car hates winter because of all that damn road salt that gets everywhere. Ironically enough, the salt helps you out too, by melting the snow and ice, and when salting trucks mix it with sand, it even gives you a little extra bit of traction on those slippery streets. But regardless, the white rocky substance is actually one of the biggest catalysts for rust. And rust is cancer to your automobile.
Short of moving to a permanently warmer climate, there’s no avoiding the salting of your local roads. By understanding how road salt attacks your car, you can easily prevent the slow, consuming creep of rust throughout your metallic investment. If your time and money are anywhere near as precious to you as your car, it’s worth the short chemistry lesson.
You can park a car in the middle of Death Valley or the Atacama, and it’ll rust. No matter how arid the atmosphere is, it will eventually happen. Especially the iron parts; iron will happily hand over its electrons to oxygen molecules (the process of oxidation), no matter the environment. If water joins the party it brings more oxygen molecules, thus adding fuel to the proverbial fire.
When salt is thrown on an icy or snow-covered road, it lowers the freezing temperature of H2O and melts the snow and ice, which is sprayed all over your car by traffic and your own tires. But it’s not as simple as snow meets salt, water meets car, boom, rust.
When road salt — sodium chloride — dissolves in water, the one-to-one ratio of sodium ions and chlorine ions break apart evenly, lowering water’s freezing point and transforming into free ions that the iron molecules love. In a sense, salt turbocharges water’s effect on metal. Other powerful road salts made of calcium chloride and magnesium chloride have even more ions to give iron, making the rusting process incredibly more aggressive.
Other contaminants and impurities in water, when combined with road salt, can also create mild acids and accelerate the oxidation process further.
All this causes plain old rust, or iron oxide, whose molecules take up more space than regular iron molecules, so the oxidation process spreads. The only way to stop that process is to remove the rust altogether. Pro tip: don’t let it get that far.
Here’s How to Stop Rust Before It Starts
Before, During and After Snowstorms
Wax on, keep the rust off. Spray from the road is filled with salty terror, and your paint catches a lot of it. A fresh coat of wax before winter rolls around is the easiest way to proactively protect the painted parts of your car.
Vinyl is a good investment. Vinyl wraps are a popular way to give your car the (removable) appearance of an insane paint job, but clear vinyl wraps can provide invisible protection. A full transparent wrap will cost more than a simple wax job, but it’ll show off your car’s original paint while helping to protect it.
Be proactive with a pretreatment. Most body shops and auto repair garages will offer an oil-based pretreatment to coat the underside of your car. This protective barrier will stop the salt and water from attaching itself to the unprotected undercarriage in the first place.
Weather the storm, then wash your car, rinse and repeat. It’s a good rule of thumb to wash your car after a snowstorm to immediately remove any salt. But since salt and slush usually sit on the road for the next couple weeks, it’s a smart move to take your car to a drive-through or hand wash that also has under-spray service. The quicker you get the salt off, the better.