How to Prevent Automotive Rust

By: Jonathan Strickland

Muscle Car Image Gallery Small rust spots can grow quickly and cause serious damage to your car. See more pictures of muscle cars.

Keeping your car in good working order requires regular maintenance and careful observation. One problem any motorist wants to avoid is rust. Rust not only makes your car less attractive, it can cause serious damage if left unchecked.

Rust is iron oxide, a molecule consisting of two iron atoms and three oxygen atoms. It's the product of an electrochemical process called corrosion. To create rust, three factors must be present: an anode, a cathode and an electrolyte. An anode is a piece of metal that will readily release electrons under the right circumstances. Cathodes are metals that will accept electrons. Electrolytes are liquids that facilitate the movement of electrons.


As electrons flow from the anode to the cathode via the electrolyte, the anode metal corrodes. In the case of metals with iron in them, part of the anode metal becomes rust. As the metal corrodes, it weakens. That's not something you want to have happen to your vehicle.

There are several points on your car that are more susceptible to rust. For example, your car's engine, frame, chassis, exhaust system and trunk compartment can develop rust. Optional equipment, like trailer hitches, can also fall prey to corrosion. Rust can even attack painted surfaces on your car.

Getting rid of rust is challenging. It's easier to take steps to prevent rust than it is to eradicate it. In the case of rust, an ounce of prevention is worth a pound of cure.

In this article, we'll look at the kind of conditions that can cause your vehicle to rust. We'll also look at ways to prevent rust as well as how to get rid of it if your car already shows signs of corrosion.

Conditions that Cause Automotive Rust

Because rust only needs an anode, cathode and electrolyte to form, cars are susceptible to it. The metal in your car can act as the anode and cathode. Water is an electrolyte. If the climate is humid enough, your car can develop rust even if it's under cover.

Some substances make it easier for rust to form on your car. One of the most common is salt. While water can act as an electrolyte, it's not very efficient at carrying electrons. Salt water is much more effective. An object that might rust slowly under normal conditions will rust quicker if it's in contact with salt water.


If you live near the ocean, your vehicle could be susceptible to rust due to the high salt content of the humid ocean air. But even if you live hundreds of miles away from the water, salt can still give you trouble. For example, many people use salt to get rid of ice and snow. As the ice melts, you're left with an electrolyte capable of turning your car into a rust bucket.

The primer and paint manufacturers use on cars provides some protection from rust. But if this coating is damaged from scratches or dents, moisture can make contact with the bare metal under the paint. Without the protection of the coating, your car will begin to rust.

Iron oxide forms easily and vehicles can develop rust in any region or environment. Cars in harsher environments or near oceans may be more susceptible to rust than cars in dry regions but no vehicle is completely immune.

Preventing Automotive Rust

A grinder is a useful tool when you need to remove every speck of rust from your car.
A grinder is a useful tool when you need to remove every speck of rust from your car.

When your car rolls onto the dealership lot it already has some rust protection built in. The car's paint acts as a seal, keeping moisture away from the metal in the car's body. That means you should examine and take care of your car's paint job if you want to keep rust at bay. Not only will it keep your car looking nice, but it may also prevent rust from weakening the metal on your car.

One good way to protect your car's paint job is to wash your car every two weeks and apply a wax coating once a month. Take this time to examine your car carefully. If you see any signs of scratches, bubbling or flaking, you have a problem. Bubbles can be a sign of rust forming underneath the paint and scratches or flaking can allow moisture to begin the oxidation process.


You can purchase a sealant to prevent rust from taking hold on a damaged section of your car's paint. Clean and dry the area on your car before applying the sealant -- the chemical will bond to your car's surface and you definitely don't want any moisture or dirt to be trapped under the protective coating. You may also want to purchase some touch-up paint to cover the damage once you're finished.

Drivers who live in particularly harsh environments may need to purchase a protective lubricant or anti-rust spray as additional insurance against rust. Lubricant creates an additional layer of protection. The anti-rust spray creates a seal on top of your car and acts as an extra layer of protection on top of the paint job. Before applying any sort of protective coating you should make sure your vehicle is clean and dry.

If you drive over icy roads coated in salt, you'll want to wash your car more frequently. Make sure you wash off the underside and wheel wells of the vehicle, too.

Don't forget the inside of your car, and be sure to clean up spills immediately. If you wash the interior of your car, leave your car doors open to help it dry out.

Sometimes rust can develop even when you're careful. It's easy to miss early warning signs. What do you do if your car already has rust?

Automotive Rust Repair Kits

There are a few options to consider if your vehicle already has rust. If the rust damage is extensive, you'll probably need to bring your car to a professional repair shop to replace that section of your vehicle. Treating extensive damage yourself may not be enough to make your vehicle safe to operate.

You can, however, repair minor rust damage yourself. There are a couple of different methods you can try. But before you tackle a rust repair job you should make sure you have the proper safety equipment. You should wear rubber gloves, safety goggles and a dust mask before you begin.


If you plan to scrape away rust physically, you'll need the following tools:

  • Grinder or drill with sander drill bits
  • Sanding block
  • Sand paper
  • Rivet gun and rivets
  • Hammer
  • Tinsnips
  • Body filler
  • Spreaders
  • Glazing and spot putty
  • Masking tape
  • Primer paint
  • Rust neutralizer
  • Screen wire

If the damage is minor, you may only need to sand the rust away and use some primer and touch-up paint to take care of the problem. But if rust has eaten a hole through part of your car, you'll need to grind the affected metal away and use body filler to repair the hole. Use screen wire inserted into the hole to serve as a foundation and spread body filler over the damaged area. Once it hardens, you can sand it down and apply primer and paint.

Alternatively, you can use a chemical called a rust converter. Rust converters react with iron oxide to turn it into iron tannate. Unlike iron oxide, iron tannate is stable and won't corrode the metal in your car. Most rust converters also contain a polymer that provides a protective primer over the area.

It's important to remove all the rust as you repair your car. If you miss a spot, it will continue to corrode the metal in your vehicle.

Remember to examine your car regularly for signs of rust damage. If you catch it early, repairs tend to be relatively simple and less expensive. But if you let the rust go unchecked, you may face expensive and lengthy repairs in the future.

Learn more about automotive care by following the links on the next page.

Lots More Information

Related HowStuffWorks Articles

  • CarJunky. "Car Rust Repair as Easy as Sand, Scrap and Paint." June 14, 2006. (Nov. 14, 2009)
  • Corrosion Doctors. "Rust Prevention Tips." (Nov. 14, 2009)
  • Cortec Corporation. "The ABC's of Controlling Your Car's Rust." (Nov. 14, 2009)
  • Instructables. "How to prevent rust on your car." 2009. (Nov. 14, 2009)
  • Maillie, David. "Stop car rust and prevent rust from ruining your car." 2009. (Nov. 14, 2009)
  • Ray, Crystal. "How to Prevent and Repair Rust Spots on Your Car." Associated Content. June 22, 2006. (Nov. 14, 2009)
  • Simkins, Brian. "Repair Rusted Spots on Your Car." 2007. (Nov. 16, 2009)
  • Skupeika, Markus. "Various Methods for Car Rust Prevention." Buzzle. Aug. 28, 2008. (Nov. 14, 2009)
  • The Rust Store. "Rust Prevention for Cars and Trucks (a practical guide for prevention)." 2009. (Nov. 14, 2009)
  • White, Mike. "How to Prevent Rust on Your Car." Associated Content. June 21, 2006. (Nov. 14, 2009)