Why does salt damage cars?

Road salts damage cars mostly because they react chemically with water and air to speed up the oxidation process that causes rust. If left unchecked, rust can slowly corrode the metal body of the car and can also damage the exterior paint job. Similar processes may also result in the deterioration of other materials used in critical internal components of the car, like the fuel line and brake line, which are typically located on the undercarriage. If those sensitive parts corrode, the consequences can be expensive, dangerous and could lead to a car accident.

What are the most serious risks to my car from road salt?

The most obvious damage is also often the least important: corrosion to the visible exterior of the car. While salt may cause some pitting or other damage to the paint, it's often cosmetic. More serious damage results from the salt coming into direct contact with metal – like on the car's undercarriage. The undercarriage is especially vulnerable to salt damage because it's close to the road, unpainted, and hard to see. The EPA estimates that road salt causes $5 billion in damages yearly to vehicles and roadways.

What can I do to protect my car from road salt damage and rust during the winter?

Rust formation on a car depends on so many factors that there isn't a simple answer for how long it takes for a car to develop rust. Salt speeds up the process, but your car's details (condition, options, age, etc.) play a role, as does the climate where you live, the place where you store the car, and much more. Regardless of the details, though, rust formation doesn't happen immediately, so attentive maintenance can effectively prevent winter rust and other salt damage.

One of the best ways to avoid forming rust on your car in the winter is to wash your car frequently, paying particular attention to the undercarriage and wheel wells, which accumulate salt more easily. Make sure you also dry the car well or leave it somewhere like a heated garage where it can dry effectively on its own. Leaving it wet may cause other problems if the water freezes.

One of the best ways to avoid forming rust on your car in the winter is to wash your car frequently, paying particular attention to the undercarriage and wheel wells, which accumulate salt more easily.

Consider speaking with your mechanic for a pre-winter inspection, especially if you live in an area where winter is long or salt is spread more heavily, like Vermont and New Hampshire, which lead the nation in salt usage per mile in 2020. Waxing the car before winter weather hits can provide an extra barrier to salt and can make the car easier to wash effectively. Your mechanic may offer other undercarriage treatments that help prevent salt and water from sticking, lowering the chance of problems.

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