How to Fix Rust on a Car

Rust on a car

Jae Young Ju / iStock / Getty Images

Rust or corrosion is the result of a chemical process called oxidation. Nearly everything oxidizes, including most parts of your car. Protective coatings such as varnish or paint can prevent aluminum wheels and steel body panels from rusting, but paint chips, curb scuffs, and paint cracks will eradicate the protective properties of the coating.

If you are concerned about rust on your vehicle, these steps will teach you how to fix rust on your car, as well as how to prevent it.

Steps to Fix Rust on a Car

Minor surface rust on a car can be repaired easily. If the rust is only on the surface, taking the time to fix it may prevent it from spreading and destroying your car. Generally speaking, fixing rust on a panel is a time-consuming but not complicated process.

  1. Mask off the area being repaired, protecting surrounding areas with masking tape and kraft paper or plastic sheeting. Be generous, as overspray will ruin the rest of your car.
  2. Crack off loose paint and sand down to the bare metal using 40- and 80-grit sandpaper, then 120- and 220-grit sandpapers to feather the edges of the primer, basecoat, and clearcoat. Use a dust mask to protect your lungs.
  3. Use a tack cloth to remove dust and chips, then grease and wax remover to clean dust and residue.
  4. For a smooth surface, use body filler for deeper pits, or filler primer (Step 7) for shallower pits. If using body filler, follow instructions on the filler, smoothing and sanding, returning to Step 3 when cured.
  5. Apply self-etching epoxy primer, which bonds to metal. Apply multiple light coats, allowing drying time between, then at least an hour to cure. Use in a well-ventilated garage or outside on a calm day, but not in direct sun.
  6. Wet-sand with 1,000-grit sandpaper, rinse with water, and allow to dry. Wipe with a lint-free cloth.
  7. Apply lacquer filler primer in several light coats, allowing drying time between, then at least an hour to cure.
  8. Wet-sand drips or sags with 320-grit sandpaper, then wet-sand the entire repair area with 1,000-grit sandpaper. Rinse with water and allow to dry. Wipe with a lint-free cloth.
  9. Apply colored base coat in light coats – lighter is better – allowing drying time between. If you notice dripping or sagging, sand and repaint, but otherwise do not sand the base coat. Cure at least an hour and clean with a tack cloth.
  10. Apply clearcoat in the lightest coats possible, feathering the repair area into the surrounding areas. The surface should look moist, not dripping. Lighter is better, allowing drying time between. Allow at least 4 hours curing time before driving, 48 hours before buffing, and 30 days before waxing.

On chassis parts and other parts where cosmetics aren’t as important, you can skip many of the above steps. After removing loose rust with a brush or sander, rust-converter primer can be used to stop rust in its tracks. Then, cover the primer with a quality enamel paint.

rusted out car chassis
Rust like this requires welding or replacement to restore structural soundness. Paulph04 / Wikipedia

Finally, there are times when rust repair is simply be a waste of time. If the panel has rusted through or a chassis member is flaking apart, the only way to really fix it is to replace the affected parts. Getting to the inside of body panels and chassis members is practically impossible and, in the case of chassis members, too uncertain to guarantee your safety.

How to Protect Your Car from Rust

First, protect your car by parking in a garage or carport. If this isn’t an option, consider a quality custom-fit or ready-fit car cover, which will reduce scratching of the protective coatings. Keeping your car dry also helps reduce the effect of water on unprotected surfaces.

Keeping your car clean is another way to prevent rust from taking hold. Dust, dirt, and pollen can be abrasive, scratching paint and exposing metal parts. They also hold water, which accelerates corrosion. Washing the undercarriage is critical in northern climes during snow season. Sand and ice-melt can accumulate in the undercarriage, holding water and ice-melt, accelerating corrosion of unprotected surfaces.

What about protecting those surfaces in the first place? Stone chips can expose metal, and undercoat can fall off and expose undercarriage metals. Stone chips can be easily repaired, even prevented with paint protection film, and undercoat services can be found in most areas where ice-melt is commonly used.