How to Fix Bad Rust under a Car? – Tips and Guides to Follow

Rust is a nuisance, especially when it attacks one of your biggest investments–your car! This can be difficult to correct and may even become dangerous if left unattended, but with a few tricks, you can learn how to fix bad rust under a car yourself.

You need to get the necessary tools and follow the steps to fix the rust. Step 1: Scrub the area with a wire brush. Step 2: Clean up the rust with some sandpaper. Step 3: Apply primer. Step 4: Paint over it.

You can try the steps above to fix your car, and if the damages are more than what you can repair, you should get the car to your mechanic’s workshop.

How Can Rust Happen in Your Car?

Irrespective of how careful one is, rust will eventually happen to your car. What you can do is slow the process. Any of your car underneath which is open to air and salt will suffer from rust.

 How Can Rust Happen in Your Car

However, some car types take longer to corrode than others. It has been noted that modern vehicles manufactured with strong galvanized steel resist rust more than older cars. Moreover, another important factor which plays a role in car rust is paint.

Car paint provides a form of protection to stop oxygen and water from affecting your car. Generally , if you take proper care of your car by waxing and washing regularly, you shouldn’t have much to worry about.

However, if you are using an old car or your car has accumulated a lot of rust, the best thing is removing the rust.

Tools Needed to Remove Rust from the Car

Tools Needed to Remove Rust from the Car

There are some important tools you will need if you want to fix your car rust, they are:

  • Sandpaper: This tool does a good job while scraping rust from your car. You could use a mechanical sander or sanding block tool because it is easier to use.
  • Angle Grinder: This is necessary if the rust you want to fix is many. It is durable and easy to use. Body filler. Also known as putty, this body filler paste can be used to fill holes and dents made by rust in your car.
  • Paint: You might need to paint your car underneath if you want to cover the rust surface. It is recommended you use a similar color to that of your car.
  • Masking Paper and Tape: Try to get an affordable tape or paper to cover the cracks and rusted surface.

Steps to Fix Bad Rust under the Car

After gathering the materials, next is fixing the rust in your car. To fix bad rust underneath your car, here are the steps to follow:

How to fix bad rust under a car

  • Prep Your Car: By preparing your car, you will need to bring it to a perfect location preferably a garage or outdoor place. The location must be neat, so that your car won’t accumulate dust. Then cover other parts asides the place you want to remove the rust.
  • Sand the Car Surface: After prepping your car, you will now need to remove the rust. Get a good sandpaper to scrub the affected parts of the car underneath. You will need to do this repeatedly so that all the bad rust can be removed.
  • Prime the Paint: After using sandpaper to remove the rust, get ready to paint the car. Use spray on the exposed car underneath using a new paint. Preferably, use an oil-based paint because it works better.
  • Repeat Sanding and Repainting: After using the first layer of paint, allow it to dry. Then take another 450-grit paper to smoothen the process. You will need to repaint and sand about three to four times before you can get a desired result.
  • Use a Coat: After repeating the sanding and repainting process, and all rust areas have been attended to, leave for some hours. After that you will now apply a clear coat to the affected car parts.

Important Tips to Note when Trying to Remove Rust from Your Car

Important Tips to Note when Trying to Remove Rust from Your Car

There are some important considerations you need to note. When trying to fix bad rust under the car, they are :

  • Age and Mileage of the Car: Older cars are easier to remove rust than new cars. Also, cars that run 250,00 kilometers per hour will be a bit difficult to remove their rust.
  • Cost: Check your pocket before embarking on a rust removal process. This will help you choose either to remove the rust yourself, or call professionals cleaning services.
  • Rust Type: When it comes to car rust, there are three categories of rust, they are surface scale and penetration. Surface rust on the car underneath is a mild form of rust in the earlier stage. However, if left unattended to, it will generate scale and be penetrative. The later rust types are more difficult to treat, and you might need to call experts.


Many car owners need to take care of their vehicle to prevent damage from rust and corrosion. That is why learning how to fix bad rust under a car is important. You can fix bad rust yourself or call experts depending on several factors like age, mileage and budget. The winter periods see a high surge in cars under rust because of moisture and salt.

While you can use materials like sandpaper, brush, and putty to fix bad rust under your car, preventing cars from happening to your car is the best solution. You can do this by using paints, coats or driving carefully to avoid rust

Evan Cooper

Evan Cooper

Hi, I’m Evan Cooper, the founder and an editor of this site, Doesitrust. I’m a chemical engineer and working in a rust-eliminating paint manufacturing company. Besides this profession, I’m a researcher and blogger.

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