15 Effective Ways To Stop A Car From Rusting Underneath

Car rust is one of the problems many owners may have to deal with at least once in their vehicle’s lifetime.

While rust on a car’s surface may not be a cause for alarm, you can’t really say the same for rust underneath because they are usually not easily detected till they become a huge problem. 

Quick Answer

In general, you can stop rust from underneath your car in different ways, depending on the rust level. This may involve some DIY solutions, including sanding the surface, applying a body filler, and using a rust remover, or professional help if the rust has eaten deep.

If you detect rust underneath your car early enough, driving on the road will still be safe, and you can easily repair it.

On the other hand, if rust underneath a car is left unchecked and isn’t detected quickly, it can severely damage the vehicle and cause harm to the driver.

In this case, treating the car yourself at home may be insufficient to remedy the car’s rust problem.

Therefore, you must check for rust occasionally.

Once rust appears, it is proactive to stop it from spreading or worsening.

This article suggests 15 ways to stop rust underneath your car, including DIY methods. Check it out!

How Do I Stop My Car From Rusting Underneath?

Underneath your car is at a higher risk of developing worse rust situations because it is more likely to stay wet and doesn’t get enough sunlight to dry out the moisture.

In addition, there are also many spots underneath that retain water. Since this is the case, you need to check for rust often and stop it as soon as it forms.

There are many ways to stop your car from rusting underneath, and they are:

  • Use rust remover
  • Sand the surface
  • Repair with fiberglass gel
  • Apply primer
  • Spray the base coat
  • Park your car in a garage
  • Wash your car
  • Paint the rust
  • Wax the area
  • Use a rust inhibitor
  • Use body filler
  • Replace affected area
  • Weld metal patch panel on the surface
  • Use zinc coating or galvanized metal
  • Take your car to a professional

Use A Rust Remover

Minor rust situations are easier to stop than when it has eaten deep.

This method of stopping rust works when it is still in the early stages.

You only need to apply it to the surface and leave the substance to settle in the metal for some minutes.

After it has penetrated, you can wipe off the oxidation remnant with ordinary water.

This will stop the rust from spreading or worsening and prevent rust from reappearing on the surface

However, this procedure depends on the type of rust remover you use. For example, some rust remover may require that you sand and prep the rusted area before applying it.

Once you have done that, you have stopped the rust from eating deep into your car.

POR-15 Rust Remover

If you have some rust problems on your car, you should click the link at the bottom immediately.

Time is of the essence, so get yourself a good rust remover and make rust a problem of the past!

The benefit of using a rust remover is that it requires less workforce, time, and money.

Therefore, it is advisable to always check underneath your car for rust situations. 

Sand The Surface

Another way to stop rust underneath your car is by sanding the surface. It is an efficient and easy way to stop rust from worsening underneath your car.

Sanding the surface will help to remove all the oxide buildup causing the car to rust on the surface.

This solution works for minor rust situations that haven’t tampered with your car’s integrity.

You just need to get your sanding tool from your toolbox and smoothen the surface to remove the oxide. 

However, you need to be careful and gentle on the metal when sanding your car surface so you won’t end up removing the metal.

Once you remove the oxide buildup, you have stopped the rust. 

Nevertheless, you also need to protect the surface to prevent the rust from reappearing.

In that case, you should apply some coatings to the surface to seal it.

Whatever you choose to apply on the surface should keep the metal corrosion-resistant. 

Repair With Fiberglass Gel

You can also stop rust from underneath your car by using fiberglass gel. This material is super strong as steel and can repair major structural car rust.

You will need a hardener to use with fiberglass gel. Once you have both ready, mix and apply to the rusted surface from behind.

This will strengthen the rusted surface from behind and leave the mixture to dry, and in about 15 minutes, it will begin to harden.

Then you can sand the mixture after it has fully hardened. 

If you notice excess fiberglass gel on the surface, remove it with an angle grinder and flapper wheel.

This method strengthens the metal and also stops the rust from worsening.

Apply Primer

This method of stopping rust underneath a car requires combining it with another procedure.

You shouldn’t go ahead to apply primer on a rusted surface unless you have prepped the area for repairs.

What the primer does is that it coats and seals the surface from further rust spread or from eating too deep into the car part.

Before applying the primer, you need to clean the surface you intend to cure.

Since underneath your car is prone to retaining debris, sand, and moisture, you need to rid it of those.

After wiping the surface clean, then apply a layer of primer to the surface and around the rusted area for at least an inch, so you can blend all the surface area when you are done.

Afterwards, spray another thin coat of primer over the entire surface and a heavier coat after some minutes.

When the primer dries up, sand the surface to even it out together. Then spray another coat of primer on the surface after sanding, and sand the surface again. 

Keep doing that till you have about two to three coats of primer on the rusted surface.

You can finish with a coat of paint to seal it up if you like.  

Spray With A Base Coat

You can stop rust underneath your car by spraying a base coat on the surface.

Generally, many car manufacturers spray base coats on the bottom of their newly manufactured vehicles.

This helps to prevent rust until moisture and other factors peel it off, causing the car to rust. 

Since this worked initially, it can work again to stop rust from spreading and worsening.

However, don’t start applying a base coat on the rusted area right away; you need to prep the surface.

Start by cleaning the surface; priming and sanding the surface.

After that, you can apply two or three thin layers of a base coat on the surface. 

This will help form a thick coat layer on the surface and prevents runs or dips caused by applying just one thick layer.

In addition, this will seal the rusted surface and prevent moisture from settling into the place in the future for a long time.

Park Your Car In A Garage

While this may not permanently remove rust from underneath your car, it can stop it from spreading and worsening.

The major reason you have rust underneath your car in the first place is due to moisture.

Your car could’ve picked this up from riding over wet terrains, riding in the rain, or parking over the grass where it can collect more moisture.

Not parking your car in the garage can make the rust worsen. If you leave your car outside or over wet grass, your car will soak the moisture overnight and worsen the rust.

However, you can curb rust spread by parking in the garage.

There, the temperature and humidity will be gentle on the car, ridding it of retained moisture.

This can help prevent the spread until you find a more permanent solution to remove it completely.

Additionally, if the option of parking in a garage isn’t available, you can use covered parking to protect your car from harsh elements.

Clean Your Car

This is an obvious solution and more of an obligation for every car owner. This method, like the solution above, doesn’t permanently remove rust from underneath your car.

Rather, it’s more effective in preventing rust from spreading and worsening beyond control.

Washing the area will help to remove the acid and harmful materials responsible for rust on your car.

This will be helpful if you often park your car outside or stay in a high-humidity area. 

Cleaning the rusty area will curb the spread and prep it ahead for you to apply other curing solutions on the surface.

However, if the situation is beyond surface rust, you may need a more powerful solution.

Paint The Rust

You can stop rust from spreading underneath your car, especially when the affected area is the underside of your vehicle.

According to Edward T Birdsall, painting a rusted car part makes it resistant to moisture and will materially retard corrosion.

This is another efficient way of stopping rust from worsening on your car.

However, you need to first scrape and sand off the rust and current paint on the affected area before painting it. 

In order to effectively do this, you will need an angle grinder with a flapper wheel and a wire brush to effectively and thoroughly remove the rusty surface.

You should be careful when scraping and sanding, so you don’t scrape the metal too. 

After scraping and sanding, you can use a surface rust converter to neutralize the agents that are causing the rust to penetrate deep into the metal.

Sanding will expose the metal to moisture; therefore, you need to cover the area with paint. 

Choose a paint of your choice and apply it to the surface of the now exposed area.

This provides a long-lasting effect and prevents moisture from entering the metal.

Wax The Area

Waxing the affected area can also help stop rust from underneath your car. Of course, this is another effective way to stop rust.

In fact, experts suggest you wax your car at least twice a year to prevent rust from appearing.

Before you start waxing the rusty areas, you need to wash and clean the area dry.

You need to remove the debris stuck underneath your car and the underside. Moreover, you should wipe accessible areas till they are dry.

If the area is inaccessible, you can leave the car to dry overnight.

However, remember to park the car in a covered area or garage to control humidity and temperature.

When the area is completely dry, you can apply the wax to the affected area with a pad or cloth.

Then leave the wax to dry up on the car. This will remove the rust and prevent it from reappearing for a long time.

Don’t forget to wax your car occasionally to prevent rust from returning on your car.

Use A Rust Inhibitor

If both the underneath and underside of your car are infested with rust, you can stop it from worsening by using a rust inhibitor.

This will prevent your car from further deterioration. 

Applying rust inhibitors will help to slow down the metal oxidation after exposing the area to water and oxygen.

You need to prep the area before applying rust inhibitors on the surface.

First, scrub the surface with sandpaper and wipe it off. Then, you can apply a rust inhibitor of your choice on the surface.

This will completely seal out moisture and oxygen from getting to the metal.

XIONLAB Rust Converter & Inhibitor

This magic substance not only inhibites rust, it also cuts down the prep time, because it can be applied to damp metal! Also, you can dilute it with water to make the application even easier.

Click the link below to get it right now! Your car will thank you.

Use Body Filler

Another way to stop rust from underneath your car is by using a body filler.

This is effective when the rust is mild and majorly affects your car’s underside. 

First, you need to sand the rusty areas and smoothen them.

After, you can then apply the body filler to the surface and smooth it out. 

You may need to paint the area over if you want the color to match the rest of your car.

Sand the surface, apply primer, and paint away to your satisfaction.

Replace Affected Area

Replacing the affected rusty areas is only needed when the rust situation is beyond a mild solution.

When the rust gets worse, it flakes and sheds off, leaving holes in the area.

This can compromise the car’s structural integrity and make it unsafe for riding.

Merely applying rust inhibitors may not work; therefore, you would need to replace the affected area. 

You can remove the part or panel and replace it with another if you have the strength, skill, and tools needed.

Otherwise, you can take it to a repair shop for that.

Weld Metal Patch Panel On The Surface

Another solution to serious rust situations underneath your car is to weld a metal patch panel on the affected surfaces.

You need to do this when the metal part flakes away, and there are visible holes on the surface.

First, remove the flaked parts and smoothen out the affected area.

Treating it with a rust inhibitor would be better before welding it.

Then, get your patch panels ready and weld them over the areas.

After welding the panels, you can then smoothen them out to level up with the areas surrounding the covered areas.

When you do that, it’ll feel like the part has been there all along.

Use Zinc Coating Or Galvanized Metal

Using zinc coating on rusted areas underneath your car can stop the rust from penetrating deeper.

This method is somewhat more effective and long-lasting than applying paint on the surface.

It will also prevent corrosion and rusting longer than paint. This works well for extremely rusted metal surfaces beneath your car.

It is waterproof, making it less susceptible to moisture and corrosion. 

In addition, should rust start infesting your car, it’ll affect the zinc coating first before getting to your car’s metal, thereby protecting your car from corrosion or rusting for longer. 

Take Your Car To A Professional

This solution is often the last resort for treating rust on cars.

You need to take your car to a professional when the rust situation is extremely bad, beyond your control or minor DIY repairs.

Doing that will allow a professional to examine the situation and see whether your vehicle can still be saved.

In this case, you should expect to spend a lot of money on repair costs.

Depending on the level of rust, the professional may need to replace the affected parts and apply some effective treatment on the surface.

The best option is to take your car to a professional when you have no idea what to do to repair the rust.

This will save you time. To save some money, you should visit different repair shops to get varying quotes and finally go for the repair costs that match your budget.

Final Thoughts

Rust underneath cars can be dangerous depending on the level. The good news is that you can inhibit rust from underneath your car.

Try any of the methods described in the article, depending on the level of the rust.

What’s important is that you ensure to get all rusting spots; otherwise, the corrosion will keep spreading or coming back.

However, in the end, rusting is almost inevitable in cars; therefore, you need to regularly maintain your car to prevent it from reappearing.

Key Takeaways:

  • Rust underneath a car can be dangerous
  • For serious rust situations, visit a repair shop
  • Paint, rust remover, rust inhibitor, zinc coating, and more can stop rusting
  • Regular maintenance is needed to ensure rust doesn’t reappear
  • Moisture is one major cause of rust











Jan-Lucas Ganssauge
Jan-Lucas Ganssauge