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There are many different types of car scratches. Not all of them will cause rust to form. Only scratches that expose bare metal will cause rusting.
Also, not all body panels are made of metal. Deep scratches on plastic panels won’t rust either. Not all metal rusts. For instance, aluminum body panels won’t rust.
Unfortunately, most doors, hoods, roofs, truck beds, and other exterior panels are made of steel which will rust. Front and rear bumper covers these days are almost always made of plastic these days.
Let’s go over how long it takes for a scratch to begin rusting and more importantly, what to do about it.
How Long Does It Take A Car Scratch To Rust?
Rust can begin forming almost immediately. There are many factors that determine how quickly surface rust will begin to form. The biggest factors are moisture and whether your car or truck is exposed to salt.
Moisture will determine how quickly rust will begin forming and how fast it will spread. Wet and salty environments will accelerate rusting while dry and arid environments will slow it dramatically.
How Long Does It Take For Rust To Eat Through Metal?
Just like with how long it takes rust to form, rust can eat through a car panel quickly or slowly depending on several variables. Exposed bare metal in a wet or humid environment will rust through much more quickly.
Another factor that affects the speed of rusting is heat. Unfortunately, metal that sits in direct sunlight gets very hot and will accelerate rusting. Metal panels that are next to areas of high heat such as the engine and muffler can rust more quickly as well.
Metal car panels are thin and don’t take very long to rust through. Owners of cars and trucks in the northern United States know this well due to the heavy amount of salt used during the winters to melt snow and ice.
A larger scratch or chipped paint is another factor that can accelerate. Larger areas of exposed bare metal gives rust a larger foothold to begin breaking down the metal.
While I can’t answer the question of how long it will take for rust to eat through your car or truck panel, I can tell you that you should do something to protect it from rusting sooner rather than later.
What Can You Put On Car Scratches To Prevent Rust?
Ideally, you would fix the area properly to prevent further damage due to rusting. It is possible to permanently apply a protective coating over top of the exposed metal on your car scratches without needing to going to the body shop to have the entire area repainted.
Let’s cover some of the most common solutions people use and ask about.
Will Touch Up Paint Prevent Rust?
Touch up paint is an ideal product for preventing surface rust on a freshly scratched or chipped paint. It’s a great way to permanently repair the area and prevent more damage.
It’s smart to prep bare metal by lightly sanding away any corrosion and light rust. Not removing any surface rust before applying touch up paint over top of the scratch or chip can lead to the paint failing to adhere well.
Severe rusting that has eaten through, at least partially, the metal panel should be sanded and a rust converter applied to neutralize the problem and provide a good base for touch up paint to be applied onto.
Will Clear Nail Polish Prevent Rust?
Clear or any color nail polish will keep surface rust from forming on exposed metal within a scratch on your vehicle. It will work the same way as touch up paint.
Nail polish obviously isn’t going to look the greatest, even clear nail polish, since it doesn’t help hide the scratch. But it will provide protection against rusting.
Does WD40 Prevent Rust On Cars?
It seems like WD40 is the modern day cure-all. In this case however, it isn’t a quick fix. WD40 will remove grease and oils and help clean the metal within the scratch to receive touch up paint, but it won’t prevent rust.
Does Vaseline Stop Rust?
Vaseline will prevent water and oxygen, the elements necessary for metal to begin rusting, from coming into contact with the bare metal surface.
The downside of Vaseline is that it is very temporary. Unlike touch up paint, it will wear away quickly. If you are concerned about scratches rusting before you get a chance of fixing them properly, you can protect them for a short time with petroleum jelly.
How Do You Fix A Rusted Scratch?
We have a detailed article on fixing deep scratches down to bare metal that you should check out for a thorough explanation. But the following is a great overview of the process to give you a good idea of what’s involved:
- Clean the scratch with a degreaser
- Sand the scratch with a sanding pen
- Apply touch up primer
- Apply color-matched touch up
- Apply touch up clear coat
- Polish to level the touch up with the surrounding car paint
Does Rust On A Car Spread?
If not protected, rusting will continue and eventually spread out from the site of the scratch and eat through the metal panel. This obviously will eventually compromise the structural integrity of the metal and cause you a much bigger headache than a simple cosmetic blemish.
To keep it real though, it usually takes months to years for significant rust to form. Unless you are in an environment that causes accelerated corrosion with high humidity or water exposure and salt, the process will take a while.
While the problem isn’t necessarily urgent, people procrastinate (guilty!) and can easily forget a problem they should deal with to prevent a bigger problem later. Taking time now to at least cover any scratches that could begin rusting is important because it’s top-of-mind.
Cars and trucks are expensive purchases and chances are you’re either going to keep it until the wheels fall off or you’re going to sell it to someone else. Either case means you should be doing your best to take care of your vehicle so that it will either last or provide you more money when it’s time to buy a new car or truck.
Is It Worth Fixing Scratches On Car Paintwork?
Deep scratches are worth protecting from rusting to prevent further damage to your car and paint. It’ll save you money on costly repairs later. Minor scratches on vehicles paint and clear coat that don’t penetrate through all of the paint layers are less critical.
Fixing scratches will protect your investment and increase the curb appeal. You don’t need to spend a lot of money by taking your vehicle to the body shop and have the entire car repaired and repainted.
Touch up paint can make your car or truck look great from 10 feet away without breaking the bank. You’d be amazed at the difference a little elbow grease and patience can make in the visual appearance of your vehicle.
That extra effort will be converted into extra cash in your pocket when you go to sell your car.
Paint Layers
It’s important to understand car paint layers when you’re dealing with scratches in your vehicle paint. Let’s briefly go over the different types:
Clear Coat
The clear coat on your vehicle is the top-most paint layer. It is the thickest layer of paint on your car or truck and provides UV ray protection as well as creates a glossy and shiny appearance.
These scratches are superficial and can be easily polished away. It is extremely common for these to build up over time and cover your entire car. The are not a problem but will cause your finish to look dull.
Base Coat
The second paint layer, which is directly underneath the clear, is the base coat, which is also referred to as the color coat. This paint layer provides the color of your car paint and is usually a few layers thick.
A base coat scratch is more severe than one that hasn’t penetrated the clear layer since it cannot be polished out. A scratch that exposes the base coat will need some touch up paint to properly repair the scratched area.
Primer
Primer is a type of paint that adheres well to metal and helps the base coat adhere well to the body panels. it is usually only a single layer or two thick.
A scratch that exposes primer is unusual because it is quite thin. Usually a scratched body panel that is deep enough to reach the primer will expose the metal beneath.
Bare Metal
Bare metal is the structure of your car’s exterior and what all of the layers of paint are applied onto.
Unprotected steel panels will begin rusting quickly if not protected. This is why it’s important to keep scratches that expose metal covered with touch up paint to prevent rust from forming.
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Conclusion
If you’ve ever noticed rust on your brake rotors after a rain, you’ve experienced firsthand how quickly rust can form on steel car parts exposed to the weather and elements.
Minor scratches in car paint aren’t urgent concerns. But scratches that penetrate down to the metal can cause problems later. Taking a few minutes to remove surface rust and apply a little touch up paint to protect the metal from rusting is definitely worth the time.
If you want to perform the scratch repair process to restore the look of your car or truck, it’ll take a lot more effort and patience but the end result can be pretty impressive.
Good luck and happy detailing.
