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At What Point Does a Rusty Car Become Dangerous?

A closeup of rust on the body panel of a car

Have you noticed rust on your vehicle? It’s not something anyone wants to see, but it’s definitely not something to ignore if you do. And though a little rust is to be expected over the life of a car, every big rust problem started out as “just a little,” so it’s important to pay attention and know the difference between expected wear and tear and a real problem. But at what point does a rusty car become dangerous?

Iron, man

Rust (or scientifically speaking, oxidization) is the chemical reaction between water, oxygen and metals, such as iron, so you can see how it might happen pretty easily to a car in the wild. While steel — made up mostly of iron — is a very strong material, it can literally crumble between your fingers as rust if left unprotected. Corrosive chemicals such as road salt speed up the process, so vehicles in cold and humid climates are especially prone to rust. But so are habitually dirty vehicles, since mud tends to hold moisture against the metal components.

While the issue starts as an aesthetic one, rust is a master infiltrator. Once it takes hold, it will spread if left unchecked, often hidden from view. This can compromise the structural integrity and overall safety of the vehicle both in the case of an accident and even just in daily driving.

RustorationAt What Point Does a Rusty Car Become Dangerous?

Your best bet with rust is to catch it early and address it while it’s still an easy fix. The rust damage can be broadly categorized as either surface or structural.

If you’re dealing with surface rust, congratulations. You might still have some tricky repairs ahead of you, but your safety hasn’t yet been compromised. Surface rust can be addressed by grinding or sanding off the rust completely down to the fresh metal, and then applying body filers, rust inhibitor, primer and touch-up paint.

But at what point does a rusty car become dangerous? If the rust has compromised the integrity of the vehicle, either by eating holes through the sheet metal of the cabin or by affecting the chassis, then the damage is considered structural, and greater measures must be taken. If any part of the car that bears weight or transfers force ( like the suspension, tie rods, jack points, etc.) appears to be rusted through and flakes off or flexes easily, you should look into repairs. There are frame repair kits available to assist, but you should consult a professional to make sure your repairs are sound, especially since the car may also require welding or outright replacement of affected components depending on the extent of the damage.

Getting ahead of rust

The best method for handling rust is preventive care. One of the easiest preventive steps is simply washing and waxing your car regularly to help protect it from the elements. Pay special attention to the undercarriage, especially if you live in an area where salt is used on the roads in the winter. Spending a few extra dollars at your local carwash for the undercarriage wash and treatment will go a long way toward preserving your car. You may also want to consider an undercoating for a more permanent solution. Also, keep an eye out for any small dings that might break the protective layer of paint and touch them up asap. Lastly, beware of even minor leaks inside the vehicle. Any moisture in your car gives rust an opportunity to develop.

Rust is a dangerous and invasive problem for a vehicle, but the good news is that it can be helped, the earlier the better. Taking preventive steps — and addressing rust immediately if it does appear — will save you big headaches later on.

Check out all the paint and body supplies available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on rust prevention, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photos courtesy of Blair Lampe.

Blair Lampe View All

Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter.  In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.

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