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Rusting Underneath Your Car? Here’s What To Do

rusty car

Did you discover rusting underneath your car? If so, you’re probably wondering how you can repair the problem — and what caused it in the first place. Learning how to handle chassis rust and prevent it from happening again can add years of life to your automobile. Corrosion is a daily hazard for millions of American drivers, but it doesn’t have to be a death sentence for your car or truck.

Wet, Damp and Humid

Those three words — wet, damp and humid — are the enemy when it comes to preventing rust underneath your car. The steel components in your vehicle are much more likely to corrode if they are regularly in contact with water. This is because water assists in oxidization, which is the chemical term for the reaction of iron and oxygen — more commonly known as rusting.

The underside of your car is at a higher risk of corrosion, because it’s more likely to stay wet after you drive in a rainstorm, as the sun can’t reach it to dry it out. There are also many nooks and crannies under a car that can retain water. This is especially true for any part that’s coated in moisture-soaked grime. Over time, as these areas stay almost constantly wet, that trapped water will wreak havoc on the metal of your vehicle.

Don’t Forget Salt

Road salt, or calcium chloride, is another frequent culprit when it comes to rusting underneath your car. Salt speeds up the electrolytic reaction that occurs between iron and oxygen in the presence of water, so a wet and salty undercarriage during the winter months is at an even higher risk of rusting out.

An Ounce of Prevention

Rusty screwThe simplest way to deal with rusting underneath your car is to prevent it from happening in the first place. The best way to do that is to coat the exposed metal beneath your vehicle to keep water and salt from coming into contact with it. At the factory, this is done through a process called galvanization, which covers iron components with a thin layer of zinc. You can help keep things free of corrosion by adding your own light covering of oil or undercoating, which will cling to the metal and repel water. Of course, if you really have spare time on your hands, you could get under your car and paint every bit of iron you see. Over time, however, the nicks and scratches in the paint will allow water to seep in again.

There Is a Cure

Prevention is ideal, but what do you do with rusty parts if it’s too late to stop the inevitable? If the component is too far gone, you’ll have to replace it — especially if it’s a thin body panel. If the rust is localized, however, then you can remove it with sandpaper or a grinder, apply a rust treatment, prime it and then paint it to prevent the rust from spreading. Make sure you get all of it, or the corrosion process will simply continue underneath the layer of paint.

Check out all the body and chassis parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on dealing with rusting underneath your car, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.

Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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