When it comes to automotive care, there is only so much an owner can do to keep a vehicle in top shape. For those living in climates where roads are salted to improve winter traction, some damage is simply unavoidable. Over time, salt and moisture work their way into fasteners and seams, turning routine garage work into frustration, like when a 12 mm bolt head suddenly rounds off, or worse, snaps off. At the same time, watching once-clean fender lines, rocker panels, and other salt-spray zones begin the process of rust deterioration is more than cosmetic; it’s heartbreaking, wallet-busting, and a reminder that spring and summer better be perfect to offset the harsh winters.

How Salted Roads Cause Rust

How can something so common cause so much damage? To keep it simple, road salt is typically sodium chloride and, in some regions, calcium chloride. While these salts significantly improve winter traction by lowering the freezing point of water (a great party trick to keep drinks cold in the cooler), they also create the perfect conditions for corrosion. As Dusty and Rusty Rust-eze (voiced by the Magliozzi brothers) remind us in Pixar’s Cars, all that salt and grime can rust your bolts and freeze your…plans in the garage.

When salt dissolves in water, it forms an electrolyte. Unlike the sports drinks used to replenish electrolytes in the human body, this solution allows electrons to move more freely between metal surfaces. That increased electron flow accelerates electrochemical reactions, specifically oxidation, which leads to faster breakdown of protective coatings and corrosion elsewhere.

Unfortunately, the damage does not stay on the surface. Once corrosion begins, rust tends to spread and burrow inward, penetrating deeper into the metal rather than remaining superficial. This aggressive and progressive behavior is why rust is often described as “cancerous” in most automotive groups. It spreads, weakens the surrounding material, and worsens over time if left untreated. Chances are, if you’ve shopped for classic cars or trucks, you’ve seen the kind of devastation that can happen in the north. Salt exposure can also accelerate galvanic corrosion when dissimilar metals are used together, such as steel fasteners threaded into aluminum.

As corrosion forms, it also expands. Iron oxide can occupy several times the volume of the original metal, forcing fastener threads outward against their mating threads. This expansion increases friction and effectively locks the bolt in place. As a result, a seized fastener is not always about applying more torque. It often requires a lot of patience, heat, penetrating oil, creativity, and a few thrown wrenches for good measure.

What Can You Do to Prevent Rust from Salted Roads?

Aside from moving somewhere warmer or finding a city that has switched to sand, it’s difficult to avoid driving on salted roads. What you can do is limit the damage salt causes with a few simple, preventative steps. While it takes some effort, rust prevention comes down to reducing salt buildup, limiting moisture retention, and protecting exposed metal before corrosion has a chance to take hold.

The most effective and obvious step is removing salt from the undercarriage. Regular washing makes a huge difference. Many car washes offer an undercarriage spray, but this can also be done at home without a lift or a jack. High-pressure undercarriage sprayers slide under the vehicle and allow you to rinse away salt and grime where it does the most damage. You can even add the extra help of a leaf blower to push fluids off. If you’re brave enough, this can be done any time of year, even in winter. Focus on the wheel wells, suspension components, and frame. Pro tip: Hot water is not required, but your hands will appreciate it. 

As discussed in our Beyond the Basics article, trapped moisture accelerates corrosion and decay. Salt becomes especially destructive when it sits in hidden areas. Clearing any drain holes of leaves and debris allows salty water to escape instead of pooling where it quietly eats away at metal. Check body drains, frame drains, and rocker panel holes to make sure moisture has a way out.

A little preparation goes a long way. For winter protection, paint protection film can act as a durable, sacrificial barrier that shields paint from ice, snow, and salt spray. Lanolin- or oil-based underbody coatings can also slow corrosion by creating a moisture barrier. Rubberized coatings can help as well, but only when applied to clean, rust-free surfaces. Spraying rubberized coating over existing rust simply traps moisture and allows corrosion to continue doing its thing out of sight.
If you are already working on the vehicle, adding a small amount of anti-seize to fastener threads during reassembly can make future repairs far less dramatic. This is especially helpful on suspension and exhaust hardware, where exposure and heat cycles are unavoidable.

Finally, the same logic of battery health in cold weather seen in this newsletter also applies to rust prevention. Short winter trips are hard on batteries and corrosion protection, but vehicles that sit unused for long periods often suffer even more. Regular driving helps evaporate moisture and reduce the time salt and water sit on the chassis. In other words, driving the car doesn’t just keep the battery alive - it helps prevent rust from settling in and getting comfortable.

A Little Effort Now Saves a Lot of Swearing Later

Salted roads may attempt to keep cars on the road in winter, but they also guarantee that future repairs will test patience. The next time a fastener comes loose instead of snapping, or a suspension bolt backs out instead of rounding off, you will be glad you took the time to fight corrosion early. Winter might win a few battles, but with the right approach, it does not have to win the war.