What Causes Rust Under Cars? [Know Ways to Prevent It]

Rust is one of the biggest enemies of cars. Rust can cause extreme damage to your car’s metal components and parts, sidewalls, floor panels, and other areas. One of the biggest concerns that owners should have regarding rust is on their undercarriage. However, you should know what causes rust in cars so you can find the right way to fix it.

The biggest causes of rust under a car are water and road salts. If a car is often parked in an environment with these elements, rust will develop over time. Although rare, it’s also possible for rust to form from accidents that damage the vehicle’s frame.

Also, aged cars are prone to rust because the resistant coatings tend to wear off over time. Moreover, if you don’t have a basement or garage, your car may also suffer from rust when exposed to harmful air pollutants.

When rust eventually occurs in your car, you can slow down this process by using various rust preventive methods that offer protection for your car.

New cars have better protection because they come with a galvanized coating that prevents rust.

Major Causes Of Rust To Cars

Major Causes of Rust to Cars

Here are the major things that can cause rust to your car:

  • Water: There is virtually nowhere in Western nations that don’t experience any form of rain or the other and this can be a problem for car owners. Those without garages and who leave their vehicles outside will probably have their cars suffering from rust. You could dry your car immediately before the rain stops or let it undergo a form of covering.
  • Bad Weather Conditions: When your car stays exposed to heat, snow and moisture for long, it is prone to suffer from rust.
  • Location: Those who stay close to beaches and rivers should expect their cars to corrode easily.
  • Road Salt: One of the key causes of rust in cars is road salt, this is why sea waters cause corrosion easily. Chemical reactions which cause corrosion do so easily with road salt.  The remnants from this snow always find their way into the car under.
  • Poor Maintenance: Giving your car proper care is important because it has reduced the rust process. However, many car owners neglect their vehicles, making it easy for rust to take place.
  • Driving Style: An underrated cause of rust in a car is driving style. Those who drive well and adhere to common driving rules suffer less from rust. However, many are careless drivers who suffer from scratches. Scratches open up your cars to elements which accelerate rust.

How To Easily Spot Rust In The Car Under?

Prevention, they say, is better than cure. If you can learn how to spot rust in time, you can remove it before it spreads to other car parts.

How to Easily Spot Rust in the Car under

To spot rust easily, do the following :

  • Always Check Your Car for Dents and Scratches: The most common opening for rust to occur is where there is a dent. This is because it leaves the car open to elements which can cause corrosion.
  • Look for Little Bubbles under the Car Paint: These small bubbling paints are what you should look out for to check rust. Anytime you spot any bubble, act on it immediately to prevent rust from spreading.
  • Be Careful when Dealing with Used Cars: Finding rust on your car isn’t that complicated if you know where to look. But, if your aim is to buy a used car, you have to be careful. Check body works, panels and other interior body under parts.

How To Stop Your Car From Rust And Corrosion?

The best way to deal with rust and corrosion is prevention. Here are some ways to prevent rust from your car under:

How to Stop Your Car from Rust and Corrosion

  • Covering Your Car in the Garage: Keeping your vehicle in a basement can prevent early rust. This will cover it up from harsh weather conditions which accelerate rust.
  •  Washing Your Car Undercarriage Regularly: Keeping your car and its undercarriage clean from dirts, salts and grits will help prevent rust from happening to your car. When washing your car, always pay special attention to inners and exposed areas which are susceptible to rust.
  • Deal Quickly with Small Rust: When you notice any parts of your car that have little rust spots, immediately deal with it. Surface rust is easier to deal with than when it becomes penetrative rust. Using an anti-primer and brush will remove small rust from your car before it spreads.

Steps to Remove Rust from Your Car

When your car gets rusty, get materials like soap, sandpaper, iron sponge, and paints. Then follow these steps to remove rust from your cars:

Wash the Affected Parts: Before starting the process, you will need to properly clean the areas of your cars that rust. By doing this, you will remove all dirt and contaminants there. After washing, leave for about three hours for the part to dry properly.

Wash the Affected Parts

Isolate the Affected Part Immediately: Rust is known to spread quickly like bacteria. You will need to keep it locked down where you find it. This prevents it from spreading to other parts.

Use a Rust Removal Product: You will need to get some good rust removal products or lubricant to spray the affected areas. While WD-40 and lime-a-away are good suggestions, there are other less popular rust removal products. Whichever you buy ensures you follow the directions as stated.

Use a Rust Removal Product

Use Sandpaper to Remove Remnants of Rust: If you follow the above steps judiciously, you should be able to remove most of the rust. However, from those who use spray rust lubricants, there might be small rust droplets which you will need to remove using grease and sandpaper.

Clean with an IPA Solution: Although this is optional, it is an ideal rust solution which removes dust and other pollutants from your car.

Spray a Primer over the Affected Car Parts: After you have scrubbed the rust away from the parts, you should spray the area with a paint primer. This ensures that you cover the scrubber area with similar color and makes it better facially.


Cars are prone to suffer from rust, especially when exposed to elements like salt, air and water. Knowing what causes rust under cars will help you know how to prevent and remove the rust.

You can prevent rust from underneath the cars by parking in a garage, using the right coating, and improving your driving style. When your car is affected by rust, you can remove this rust using materials like sandpaper, brush, and primer paints.

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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