Paint decontamination

How to Keep Rust Off Your Car's Paint

rusty old car

Rust is a nightmare for every car owner. It’s also one of the most common issues car owners face, and one that needs to be taken very seriously.

If you’ve noticed bubbles under your paint, stains and other surface irregularities, dampness on the floor after hitting a puddle, chips and dents on the vehicle’s body - chances are you are battling rust too.

Dealing with rust is a task that requires a lot of elbow grease, but it’s necessary. Not only that - it must be done as soon as possible.

This is because the corrosion process on vehicles doesn't just ruin their appearance by turning the paint an odd orangish-red color. When oxidation takes place, the atoms making up the metal in your car start to detach from their connections, breaking down to dust.

That’s scary. But don’t worry!

There are a lot of things you can do to reduce the likelihood of rust occurring on your ride. As with most things, it’s easier to prevent this problem than to fix it. But if you already spotted rusty spots on your car, that doesn’t automatically mean it’s doomed to a junkyard.

Think of rust like a disease - one that’s attacking your investment. The earlier you catch it, the easier, faster, and more affordable it is to treat it.

If you leave rust on your car unattended, its damaging effects will lead to costly repairs. In some cases, you may even have to get a new ride. And if you try to sell your rusty car, its value will be significantly decreased. Nobody wants to invest in a vehicle with corrosion problems because while small rust repairs don’t cost much, larger ones can cost from $200 up to $2,500 or more.

If you want to do everything you can to protect your prized possession from rust, you should understand why cars become rusty, what types of rust are there, which parts of vehicles are most problematic, how to prevent rust & what to do when it appears.

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What is Rust?

Rust, short for “red dust”, is a chemical reaction that happens when ferrous metal molecules come in contact with oxygen in the presence of moisture. The process of oxidation causes the electrochemical breakdown (called corrosion) of metals that contain or consist of iron.

Corrosion occurs when an iron-containing metal is exposed to oxygen and moisture for a prolonged period of time. The thing is, ferrous metals like steel and cast iron are used in so many places due to their tensile strength and durability. Think everything from supporting beams and car bodywork to cutlery and kitchenware. And while steel’s properties make it an excellent material for manufacturing cars, the impurities in it make it much more prone to rust than pure iron.

Over the years, car manufacturers have developed sophisticated measures like galvanization to mitigate rust, but they haven’t yet found a way to prevent it entirely. That’s another reason why aluminum and magnesium components are gaining popularity, apart from being lightweight. These materials corrode at rates that are unnoticeable within a human lifetime. But they’re also expensive, and as a result - automakers use them sparingly.

The truth is, rusting is an inevitable process because of iron’s unstable chemical makeup. However, the process can be delayed.

That said, the older your vehicle, the more susceptible it is to rusting - the scrapes, scratches, and dents that come with age give Mother Nature’s elements more opportunity to get behind your vehicle’s protective paintwork and attack its metal.

What Causes Rust

So, rust occurs when the water on your vehicle’s surface gets contaminated with metal particles. But, there are ways the environment and the car owners’ habits can speed up the rusting process and make it worse. Let’s go through them one by one.

Environmental Factors


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Exposure to salt is a major factor in rust formation. To put it simply, the chemical reaction that causes rust involves electrons moving around, and they do so more easily in salt water. This means that in contact with salt water, objects prone to rusting in normal conditions deteriorate considerably faster.

If you live in a northern climate, you often encounter road salt, used to remove ice. But the melting snow with salt can get stuck in your car’s underbody, in places out of your sight. If not cleaned quickly, this can cause rusting or accelerate the process if it’s already underway.

If you live in a warm, coastal area, rusting can be caused by the high salt content in the air. And even if you live in a moderate climate further inland, you can still suffer salt damage.


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Rust happens when a material that contains iron comes into contact with moisture. The most common way for this to happen is rain.

That’s why cars left in the open, exposed to the elements, have a much higher chance of becoming rusty than those kept in sheltered spots. Water gathers in certain areas like the rear tires and wheel wells. If not dried properly, these areas become particularly prone to rust.

If you live in one of the wettest states in the US, you should put more effort into protecting your vehicle well, especially during the rainy season. The reason is simple - prolonged periods of torrential rain make your car more susceptible to corrosion. But even if you reside in one of the driest states, no place stays rain-free forever.

Human Factors

Poor Maintenance

Environmental factors are one thing - if you live in certain areas of the country and don’t own a garage, there’s only so much you can do about it. But neglecting your car maintenance routine is totally on you.

Regular and proper car maintenance means you will spot rusting as soon as it occurs when it’s still fairly easy to remove. On the other hand, if you take poor care of your vehicle, it’s much more likely that a rust issue will develop and grow worse.

Washing your ride every couple of weeks and taking it to a professional at the first sign of the brown, flaky trouble, will help you stay on top of any potential rusting problems and prolong the life of your vehicle.

Bad Driving Habits

This is a factor that often gets overlooked, although it’s very important and something you can control.

If you drive too close to other vehicles, the stones and pebbles from the road fly up and hit your car. This causes chips and scratches that make it easier for rust-causing chemicals to get into your car’s bodywork.

The same goes for not paying attention to your speed when driving on newly re-surfaced roads.

Types of Car Rust

Knowing where the problem spots on your car are in the decomposition process is necessary for finding the right solution to fix them. There are 3 main stages of rust formation.

Surface rust

The first type of rust is most benign and it’s just that - on the surface, which makes it easy to spot and simple to fix.

Most surface rust on vehicles appears when their paint breaks through mechanical (dents, scratches, and chips) or UV damage (prolonged over-exposure to the sun). It can also be caused by bird droppings because of their acidic nature.

Structurally, this type of rust is not a problem, but it can become one if you don’t fix it as soon as you see it.

It’s often possible to remove surface rust using high-grade sandpaper or an abrasive wheel to grind it down until the metal is exposed. Then, the area is primed before applying new paint and a protective coating.

However, be warned: surface rust can also be just the tip of the iceberg. It’s not rare for oxidation to form inside a panel or part and work its way outward.

Scale rust

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If you don’t remove surface rust immediately, you allow for the decomposition to penetrate further into the metal. This creates a bigger problem called scale or bubble rust.

This type of rust occurs when surface rust expands and flakes away the outer layers of paint, exposing the metal underneath, which then corrodes. When that happens, the rust goes deeper into the surface, creating a rough, pitted type of damage called scale.

Fortunately, scale rust can be removed with the same process as surface rust. However, you’ll need a wire brush to make your way through the scales before using sandpaper or an abrasive wheel.

Penetrating rust

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Penetrating rust can be the cause of everything from holes in your fenders to more severe issues with frames and suspension components.

This type of rust is the most dangerous and damaging - the kind that, if left unchecked, eventually eats through your car’s metal and can compromise the structural integrity of your vehicle.

If you allowed the rusting process to get to this stage, your options are limited. In most cases, you will have to entirely replace the affected panel or have the corroded areas cut out and have patch panels welded into place. This can be done by a reputable body shop, and it can get expensive.

Where to Look for Rust

Inspecting your car for the first signs of rust is an important part of a good maintenance routine, whether you have a protective coating installed or not.

The most obvious sign of rust is exterior paint bubbling. This means the paint has lost contact with the panel underneath because water and air got in between. Other things to look out for include body damage and irregular paint. Nicks and dents should be fixed right away because they allow water and salt to permeate more quickly. Spots and strips of paint that don’t match the original paintwork could be the work of a rust repair job.

Rust can occur on any part of your vehicle, not just the body. It often appears in less visible areas, so don’t neglect your undercarriage.

Some prime rust-invasion zones on vehicles include:

  • Frame/chassis rails
  • Wheel wells and hubs
  • Tires and brake
  • Exhausts
  • Suspension
  • Windscreen
  • Trailer hitches
  • The boot’s floor
  • Trunk compartment
  • Engine compartment

Check anywhere where water is gathering or where there is exposed bare metal.

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The thing is, once rust appears, it travels through the vehicle and expands. Being negligent and ignoring the early signs of a rust issue will lead to more severe problems that will affect the look of your car and cost you a lot of money down the road.

Plus, rust can be a safety risk. So, make sure you inspect your vehicle periodically regardless of where you live, how you maintain your car, and what kind of additional underbody coating it may have come with. If you don’t want to do it yourself, ask your mechanic to do it the next time you receive an oil change or another vehicle service.

How to Prevent Rust

Even though modern cars aren’t nearly as prone to rust as those built in the 80s, you still need to take care of your vehicle well if you want to get the most out of it and prevent rust formation.

Safe Parking

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Leaving your car exposed to the elements for a longer period of time isn’t a good idea. UV rays, humidity, acid rain, snow, dirt and grime, tree sap, and other factors will damage its exterior, making it more susceptible to rusting.

The best option is to park your vehicle in a garage whenever possible. On top of that, you can try using a dehumidifier to remove any moisture in the air.

If your home doesn’t already have a garage, consider adding one. There are many solutions available even if you’re on a tight budget and don’t have a lot of space, like a portable garage. If that isn’t an option, use a vehicle cover. It won’t provide the protection of a garage, but it’s better than nothing.

Regular Washing

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We’ve established that water helps rust form so this piece of advice may seem counterintuitive.

However, washing your car regularly to remove the dirt, salt, and grime that has built up as soon as possible is the easiest way to reduce the chances of rusting. It helps you get rid of all the impurities stuck to your vehicle’s body that can cause corrosion over time.

Don’t wait for your car to look dirty before washing it. The contaminants that attack it often aren’t visible to the naked eye, so by the time you notice them, some damage will already be done.

Any type of car wash is better than not washing your car at all, but some are more effective than others. If you’re adept at handwashing techniques, you can wash your vehicle at home once a week. However, it’s still a good idea to have it professionally cleaned every couple of months.

Using a high-pressure cleaner is the easiest way to clean areas that are difficult to reach like the corners in the undercarriage and inside wheel arches. Just make sure you know how to use it properly because you don’t want to damage the paint.

In any case, dry your vehicle well with microfiber towels every time you wash.

Finishing Products

Car care products such as sealants, glazes, waxes, and coatings can help you protect and enhance your vehicle's exterior. That makes them your allies when it comes to battling rust.

Coatings are the most recent technology in this industry. They form a clear, shiny, water-repellent shield that's harder than an automotive clear coat and repels contamination, making it easy to keep clean.

If you’re hesitant about spending the extra money on a protective coating, think about the costs of rust repair if you don’t.

This extra layer of protection between your paint and the environment is a barrier that stops corrosion before it even begins. As long as you keep your car's metal well protected from corrosive salt and grime, you’ll be able to keep it rust-free for many years to come.


Rustproofing is the prevention or delay of rusting. The protection against corrosion is achieved by a process of surface finishing or treatment.

If you have a short-term lease or don’t plan to keep your car for long, you can skip this step. However, if you just bought a new car or plan to keep your vehicle around for a long time, consider investing in a rustproofing procedure. This especially applies to those who have already experienced rust issues or live in harsh environments.

There are multiple rustproofing options available today for any type of vehicle, from installing an electronic module to using drip oil spray. To determine which one best suits your vehicle’s needs, talk with your mechanic.

Bonus Tip

It’s inevitable to get snow, salt, dirt, and grime onto your car’s interior. To prevent these and other elements from getting into your carpet, get an all-weather mat. It will keep the moisture out and protect the vehicle’s floor while allowing you to remove the contaminants before they cause any serious harm.

How to Remove Rust

If you’ve already noticed rust on your car, the only way to stop it from spreading is to have it removed or completely seal the area to prevent water from entering.

The level of rust damage and where it has struck will determine if your vehicle can be repaired, and whether or not you can do it yourself. If yours is the case of scale or penetrating rust, it’s best to ask your mechanic about ways to proceed. If not, let's look at some ways of how to get rust off car paint! 

DIY Options

First off, don’t attempt to repair rust yourself if the damage is severe, if you don’t have the right tools, or if you aren’t confident in your abilities.

If you manage to catch rust reasonably quickly, while it’s still surface rust - it should be an easy fix. There are many household items that can help you remove rust without you having to resort to a chemical remover or a more complex procedure.

Here are some of the most popular DIY solutions on how to remove rust from cars:

  • Baking Soda. Apply baking soda to the rusty area and use a brush dipped in water to gently scrub the rust off the painted surface; rinse and dry.
  • Salt and Lemon Juice. Sprinkle some coarse salt onto the rust, then add lemon juice. Let it sit for a bit, but not too long; wipe off, rinse, and dry.
  • Distilled White Vinegar. Submerge the rusted object in undiluted white vinegar and allow it to soak for 30 minutes. Scrub off the rust, rinse and dry.
  • Coca-Cola. Soak a sponge in Coca-Cola and scrub the area; rinse and dry.
  • Dish Soap and Potato: for delicate surfaces, cut a potato in half and dip it into a bowl of dish soap; apply to the painted surface and rub away the rust.
  • WD-40. Spray the corroded areas following the instructions carefully and keeping the product away from the tires. Wait 10 minutes and then scrub the surface lightly with a brush; rinse and dry. For extra protection, apply another layer of WD-40 and wipe down with a clean cloth. This will act as a temporary barrier to rust formation in the future.
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  • Sandpaper. You will need safety gear for this one - goggles and a mask. Choose very fine or medium sandpaper to minimize the damage to your paint. Even if you are very careful, it will probably need a touch-up afterward.

Pro Options

If the rust does not come off with any of these procedures, you should consider professional solutions. These include:

  • Sprays. Rust removal sprays are a convenient and non-aggressive way to get rid of rust without breaking a sweat. Undrdog Iron and Fallout Remover, The Purps, works like a liquid clay bar, dissolving embedded contaminants that can cause future damage to your vehicle's paint and metal surfaces. This way, it prevents the premature failure of the vehicle’s clear coat.

Your car picks up little bits of contamination during the course of its life on the road. Undrdog Iron Rust and Fallout Remover works like a liquid clay bar, dissolving embedded irons and contaminants that can cause future damage to your vehicles paint and metal surfaces. This product is fantastic to use when prepping to coat your vehicle. Your car picks up little bits of contamination during the course of its life on the road. Undrdog Iron Rust and Fallout Remover works like a liquid clay bar, dissolving embedded irons and contaminants that can cause future damage to your vehicles paint and metal surfaces. This product is fantastic to use when prepping to coat your vehicle. 

  • Clay Bar. Detailing clay is a flexible resin compound designed to remove contaminants that become lodged in clear coat paint. It requires no special tools or equipment and can remove what paint polish can’t. However, claying is a time-consuming process and can lead to paint damage.
  • Wet Sanding. Sanding is an advanced technique used to fix a range of cosmetic issues a vehicle might have like scratches, rust spots, cloudy headlights, and gel coat cracks. However, it’s an “aggressive” solution that requires you to have the right skills and be properly equipped for the job. You’ll need an angle grinder, wire brush, orbital sander, cordless drill, sandpaper, metal primer, paint, and rubbing compound - among other things. If this sounds too complicated and you want to spare yourself the hassle - get your vehicle wet sanded by a professional.

Step-by-step Instructions

If you inspect your vehicle for rust regularly, you will notice the early signs of rust formation. This means you will be able to remove the rust and prevent further damage to your car in the simplest way possible - with an Iron and Fallout Remover.

Undrdog Iron and Fallout Remover is a breeze to use. Let’s go through the steps together:

Step 1 - Wash

Wash your vehicle in the shade using Undrdog Soap to remove any dirt build-up.

Step 2 - Spray On

While the vehicle is still wet, spray The Purps on the paint and wheels, avoiding plastics.

We do not recommend diluting it as this method is not going to be more cost-effective. You may end up with a surface that is not properly decontaminated, which will ultimately mean you will need to reapply the product.

Step 3 - Let it Dwell

In about 2-5 minutes the paint will begin to turn purple where there are iron contaminants embedded.

Attention: do not allow the product to dry on any surface of your vehicle.

Step 4 - Rinse Off

Rinse well and wash away the embedded contaminants.

The Purps is a very potent product and you probably won’t need to repeat the process. However, when dealing with severe contamination, it’s better to make sure you got it all out. 

To check, spray the product again on a section of the vehicle that was most affected, and observe if there is a reaction. If not, you’re good to go!

Here's a quick video we made about the process: 

To Sum Up

Car technology is advancing faster than ever. Because of this, modern cars combat corrosion much better than older ones. However, rust can still occur, and when it does, you should tackle it as soon as possible. Otherwise, over time, your prized possession can become nothing more than a worthless pile of metal.

We can’t stress the importance of this enough: check your vehicle for rust regularly.

On the plus side, rust is a largely preventable problem. By keeping your car indoors, sticking to your maintenance schedule, and investing in a protective coating and rustproofing procedure, you will drive a rust-free car for years to come.

And even if you let some surface rust slide, it’s not the end of the world! There are many DIY rust removal methods you can try, and a couple of professional ones that will help you rid your vehicle of rust and protect it from future damage.

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