In cities with snowy winters, road salt is often the first line of defense against icy roads. When spread on snow and ice, salt reacts with it to lower the water's freezing temperature and keeping it liquid despite cold conditions. This prevents roads from becoming dangerously slippery. Unfortunately, road salt's reactive properties also wreak havoc on the cars driving over it. Salt splashed onto car bodies quickly leads to rust. Taking a few protective steps before and during the winter can save your vehicle's undercarriage from extensive damage.
Wash your car very thoroughly in late autumn. This will allow for a coat of sealant to be applied to the undercarriage and wax to the body without trapping materials that will encourage corrosion.
Spray your undercarriage with a sealant. This can be applied by professionals at a garage, or at home. Spray sealants are available at most automotive stores, especially in areas with road salt use. Pay extra attention to the brake and fuel lines when applying sealant, since these are the parts of the undercarriage most vulnerable to corrosion from road salt. They also prevent a serious safety risk if they fail.
Wash your vehicle often during the winter. You should try to wash your car at least every 10 days. Many car washes offer undercarriage washes and steam cleanings, especially during the winter when road salt is in use. Wash your vehicle as soon as possible after any snowfall, and whenever the temperature gets above 40 degrees. If you wash at a carwash, avoid those that use recycled water, as it will likely be quite salty.
Avoid driving through puddles of standing water. In wintertime, these puddles will be heavily saline and will easily splash up into your undercarriage.
Clean your tires regularly to make sure they aren't carrying wet leaves or other materials that hold water. This water could be sprayed into your undercarriage, leading to rust.
