This post may contain affiliate links which means I may receive a commission for purchases made through links.
Many new cars leave the factory with some level of rust protection to keep them roadworthy for several years to come. However, if you take a peek underneath your used car, you’ll either see a thick coating of primitive underseal or worrying signs of rust forming.
That’s because the car’s underside is subjected to a lot of wear & tear due to its proximity to the road surface. Not to mention that stones flying underneath the car while driving chip any protective coatings it may have, exposing it to water, salt, and other contaminants that promote rust formation.
Failing to stop or prevent rust-related damage will affect the structural rigidity of the car’s floor panels and critical suspension components, costing you a lot of money in the long run. With the best undercoat paint to protect your car from rust though, you can easily give your car’s underbelly maximum protection against corrosion.
But, how do you even identify the best undercoat paint to protect your car from rust? Well, this guide has some incredible options for you.
First, let’s look at how an underseal works!
How an underseal/ Underbody Protection works
To start, an underseal is a wax- or rubber-based substance that is designed to be sprayed on the car’s underbody. However, it can also be used elsewhere to protect metal surfaces from rust and corrosion.
That said, an underseal/ undercoat paint builds up a protective layer on the car’s underside. In essence, it works as a thick protection layer that ensures stones and rocks bounce off the car’s underside.
More importantly, underseal paints prevent rust build-up and cover up the existing rust. Specifically, an underseal acts as a barrier against salt, moisture, and other harmful elements that can cause corrosion and rust to occur in the car’s underbody.
This plays a crucial role in protecting important structural parts of the car like suspension mounting points away from salt, water, and debris that might lead to the formation of rust and corrosion.
One thing you need to note though is that there are several types of undercoating in the market, making it a bit difficult to choose the right one for your needs.
Hopefully, the buying guide will help you identify the most important factors you should consider while selecting the best underseal for your car!
Buying Guide (Important Factors to Consider when Choosing the Best Undercoat Paint for Cars)
Removing rust in your car’s underside and applying a new layer of undercoat is a great way to prevent further corrosion from happening. Unfortunately, finding the best undercoat for your project isn’t always an easy task, especially considering the wide range of products on the market.
The following factors might help you find the best undercoat paint that will suit your project needs:
Type of underseal paint (formulation)
As mentioned earlier, there are various types of undercoating paints in the market. The most popular options are:
The formula of this type of underseal paint contains oil and forms the strongest coating of any other underseal paint. For that reason, it’s commonly used in new cars before they leave the factory to protect the car’s underbelly against debris and salt damage.
The rubberized undercoat is one of the most popular types of underseal paints due to its durability and ability to provide additional sound dampening. In addition, it has a thicker formula that forms an excellent barrier against corrosion and weathering elements.
Not to forget that it’s relatively easy to apply since you can spray it on various surfaces without leaving a mess.
Overall, it’s the best option for protecting your car’s undercarriage as it offers the easiest and best protective measures against moisture and rust. Even better, it’s also safe to use on quarter panels and wheel wells and can be painted over in case you use it for bodywork.
Paraffin or wax/ water-based undercoat
Wax-based underseal is the most popular type of undercoat paint for cars due to its affordability, easy application, and fast-drying formula. For that, it’s a perfect option for DIY projects as it’s relatively available in various stores.
Plus, it easily gets into all the seams and cracks on the car’s underbody.
On the downside, you have to apply this underseal paint more frequently compared to other types of formulas since it’s not that durable. Moreover, you need to apply multiple coats to form a thicker barrier for extra protection.
Other than that, it provides base protection in moderately humid areas and warm climates where salt and other harsh debris are not on the road.
Commonly referred to as military-grade underbody paint, asphalt-based underseal is the strongest option as it’s intended for large vehicles like trucks. It provides extra durability and protection against moisture, chips, and rocks.
As you would expect though, it’s very pricey as it’s available in 5-gallon containers and requires some skills to apply. Also, it’s not paintable and needs more curing time compared to other types of undercoating.
All in all, it’s a great option for heavy machinery and large trucks.
Polyurethane undercoat paint
Polyurethane underseal paint usually comes in large cans and can be applied using car paint spray guns. During application, it forms a chemical bond that protects exposed metal surfaces in your car’s underside, while covering any gaps and cracks.
Unfortunately, you need to sand the surface and apply an etching primer to bare metals before you use this undercoat paint, making it more time-consuming. On the bright side, it sands quickly and can be painted over if you need to perform bodywork.
Apart from the type of undercoating product, you need to consider the volume or amount of the paint before you settle on any option. Here, you need to think about the amount of undercoat you’ll use, car size, and the amount of paint you might want to buy in the near future.
In most cases, car undercoating products are available in various sizes ranging from 16 oz to 5 gallons. A 16-oz spray bottle may contain enough paint to cover a small car, while trucks and RVs will need at least 1 gallon of the underseal paint to get the job done.
Ease of application
Generally, you have two options when buying an underseal paint for your car; a normal gallon bottle and a spray bottle. Make sure you have an undercoating paint gun if you’re planning to buy the 1-gallon undercoat paint.
However, if you don’t have a spray gun, I’d recommend you choose an underseal paint that comes in a spray bottle/ can as it will be easier to apply. However, using a paint spray gun is always the preferable method of applying undercoat as it makes the application simple and durable, especially in hard-to-reach areas.
Black Vs Clear Undercoat Paint: Which is better?
An underseal paint that offers a textured black finish is highly desirable as it hides many unwanted defects while providing a finish that matches the OEM finish. For that reason, the black clear coat is the most popular type of undercoating among many car owners.
However, choosing between a Black and a Clear coat is usually a matter of personal preference.
7 Best Undercoat Paint for cars
1. WoolWax Automotive Undercoating Paint
First on our list is this vehicle undercoating from Woolwax, which is an excellent option for automotive use, battery terminals, boat trailers, garage door tracks, as well as heavy machinery.
In short, if you’re looking for the best undercoat that is ideal for automotive use and marine environments, it’s the perfect product for you!
This undercoating is made from a naturally occurring wax known as lanolin that is secreted by wool-bearing animals like sheep. More notably, this formula is environment-friendly and non-toxic as it doesn’t contain any solvents.
Even better, the lack of solvents prevents it from evaporating over time, giving your car longer protection against corrosion and water after application.
One of the most interesting features of this undercoat is that its formula is thick enough to prevent dripping. At the same time, it’s fluid enough to spray with one of the proprietary spray gun designs with 70 to 90 PSI.
Unfortunately, you have to buy the sprayer separately as it doesn’t come included in the package.
Another notable drawback of this formula is that it;’s a bit pricey compared to other undercoating paints on our list. Other than that, it has an odor-free and non-conductive formula, so it will not harm any electrical connection in your car’s underside.
After application, this undercoating cures and hardens to a gel-like consistency. As a result, it stays flexible after curing, allowing it to ‘heal’ itself in case the coating is scratched.
- Doesn’t wash off easily
- Little to no smell
- Contains no solvents to reduce evaporation
- Environment friendly
- Comes in a 1-gallon can
- A bit pricey
- Requires a proprietary spray gun at an extra cost
2. Rust-Oleum Pro-Grade Rubberized Undercoating
Rust-Oleum is a reputable brand in the car corrosion industry that has been around for over 100 years. Interestingly, the company was created after discovering that oil spilled on a boat’s metal deck inhibited rust formation.
Therefore, you can rest assured that its Pro-grade rubberized undercoating is good enough to protect your car’s underside against rust damage and other contaminants it comes into contact with while on the road.
In addition, this makes it ideal for use in harsh marine environments and for protecting cars from winter road salt. Specifically, it’s designed for use in car underbodies, trunks, and wheel wells to deaden sound and form a strong barrier against corrosion.
In terms of packaging, this undercoating comes in a 15 oz spray can that contains enough paint to cover an area of about 10 – 15 sq ft.
Better yet, the spray can is equipped with a wide all-angle nozzle tip, allowing you to paint primed or bare metal surfaces of your car even when the can is upside down.
Once applied, this formula lays down nicely to produce a smooth low-luster finish, especially if you apply many light coats. More importantly, it covers most surface rust effectively and dries evenly within 60 minutes, even if you overspray in some areas.
- Provides rust protection
- Reduces road noise
- Easy to spray at any angle
- Dries quickly (60 minutes)
- Delivers a black finish
- Professional rubberized undercoating
- Requires multiple coats for good coverage
3. 3M 03584 Rubberized Undercoating Paint for Cars
Manufactured by another reputable brand in the automotive protection industry, the 3M 03546 rubberized undercoating spray can effectively remove any traces of abrasion, dust, and corrosion from your car’s undercarriage.
The spray goes on the surface black but dries to form a rubberized, flexible coating that will protect your car’s metal from rust-causing salt and other road hazards.
In addition, similar to many undercoating products, this formula offers some sound deadening. Therefore, your car will be a little quieter once you apply it to the vehicle’s underside.
At the same time, the undercoating seals up small holes and cracks in your old undercarriage to even out the surface.
However, before you spray this undercoating on the intended surface, make sure you clean and dry the area first. Interestingly, you don’t need to primer the metal surface first as you would when painting it.
It’s also worth mentioning that this product comes in a 6-pack of 16 oz spray cans, meaning you’ll have enough paint to coat the entire underside of a small car.
Plus, you can also use it on trunk lids, wheel wells, under the hood, quarter panels, and on the interior side of the fenders.
- Comes from a reputable brand
- Removes rust effectively
- Available in convenient 6-pack of spray cans
- Dries smooth within 30 minutes
- Incredible sound-deadening properties
- Ideal for cars, RVs, and trucks
- You need to apply a lot of paint for better results
4. POR-15 Rust Preventive Coating
As the name suggests, this POR-15 undercoating is specifically designed to permanently stop rust on your car’s underside.
All thanks to its ability to form an impenetrable barrier that protects various surfaces from salt, chemicals, water, and corrosive contaminants, making it a popular option among DIYers and professionals alike.
Better yet, the formula creates a rock-hard, non-porous finish that is highly resistant to peeling, cracking, and or chipping. On the same note, it’s resistant to alkalis, and acids and repels oils and fuels.
Not to forget that you can use it directly on a seasoned car body. Also, it’s ideal for use on sandblasted and prepped rusted metal surfaces.
To apply this formula, it’s recommended that you use a POR-15 water-based degreaser followed by POR-15 Metal prep to clean the surface and neutralize rust. Next, apply at least 2 thin coats of the formula and leave it for 2 – 5 hours to dry before you apply a topcoat.
Surprisingly, unlike most car paints that dry through evaporation, this undercoating cures faster in the presence of moisture.
On the downside, this formula is sensitive to UV light. So, make sure you cover it with a top coat if the surface you’re applying it to will be exposed to sunlight.
- Suitable for use on any metal surface
- Forms a non-porous coating
- Can be used directly on the seasoned or rusted surface
- Prevents rust effectively
- Cures faster in the presence of moisture
- Sensitive to UV light
- Messy application
5. Fluid Film Rust and Corrosion Protection Undercoating
For those who need a large volume of undercoating paint, this high-quality product from Fluid Film is the best option for you. According to the manufacturer, this undercoating was designed for industrial applications, mainly for use on offshore oil rings and large ships where corrosion is a major problem.
Therefore, you can rest assured that it will effectively protect your car’s underbelly from rust and other elements that cause surface oxidation.
However, that’s not the only good thing about buying this rust & corrosion protection undercoating.
First of all, this paint comes in a huge 5-gallon (18.92 L) pail. However, you can find it in a spray can option or 1-gallon containers for use in small areas.
That aside, this undercoating features an eco-friendly, Lanolin-based formula, making it safe to use without harming the environment.
Plus, it contains antifreeze elements to increase its durability and make it easy to use during cold weather. However, it’s recommended that you apply this underseal in warm weather when it’s in its most fluid taste as its formula is quite thick.
Talking of application, this undercoating should be applied through a spray gun for better results. Besides, this allows you to cover larger areas and get to the tight areas more efficiently.
The only drawback with this formula is that it has a strong odor, so you’ll need a respirator when applying it. Other than that, it provides excellent corrosion protection to your car’s underside and salvages significantly corroded & frozen parts, including nuts & bolts.
- Repels water, ice & snow while retarding rust
- Provides optimal coverage to the vehicle’s underbody
- Environment-friendly formula with natural ingredients
- Contains an antifreeze formula for extra protection during cold seasons
- Available in 1-gallon and 5-gallon size options
- Leaves a clear finish after curing
- Requires a separate spray gun to apply this undercoat
6. Penray 4424 Rubberized Undercoat paint for cars
The 4424 Rubberized undercoat from Penray Industries is another great product for protecting your car’s undercarriage from rust, corrosion, moisture, heat, dust, and other elements that cause damage.
Interestingly, even with its exceptional ability to form a protective layer that protects your car’s underside from harsh weather elements, it’s relatively affordable.
Better yet, it forms a waterproof and highly durable protective layer once it dries.
On top of that, this formula is very easy to use and apply as it comes in a convenient 16 oz aerosol can. Even better, the formula does not leave clumps or drips during application and can even be painted over with no bleed-through.
This makes it ideal for various automotive applications like painting wheel wells, frames, and undercarriage. In addition, you can use it for minor repairs on gutters and repairs and on home foundations.
Unfortunately, despite being easy to apply, this rubberized undercoat requires multiple coats for better results, meaning you may run out of the 16 oz can before you complete the job.
Apart from that, it’s ideal for use on trailers, cars, RVs, and trucks as it acts as an insulator to reduce road noise.
- Quick-drying formula
- Ideal for all automotive applications
- Reduces road noise
- Forms a waterproof coating
- Can be painted over
- Requires multiple coats to get the job done
7. Dynatron 544 Dyna-Pro Rubberized Undercoat Paint for Cars
Despite being ranked last on our list, the Dynatron 544 Dyna-Pro is another great undercoat for protecting your car’s underbody from rust. Plus, it provides all-weather protection and it’s very durable that it can last through the entire winter season.
Not to forget that the Dyna-Pro formula is even backed by popular brands like 3M.
However, unlike the 3M undercoat we reviewed earlier, this formula comes in a 1- or 5-gallon can instead of an aerosol can. For that reason, you can either apply it with a brush or a spray gun.
As mentioned earlier though, I recommend using a spray gun to apply this formula to speed up the painting process and get better results.
Interestingly, this undercoat forms a fast-drying coating after application and matches any desired OEM color, while leaving a smooth feel even on rusted surfaces.
More notably, it forms a strong and durable barrier against chipping, rust, and weathering, and reduces the road noise from the undercarriage.
As for the downside, this undercoat does have great adhesion on older undercoats or greasy surfaces. So, make sure you clean and prepare the surface before you spray this formula on the surface.
More importantly, this formula is not available for consumer sale as it’s intended for occupational/ industrial use only. In addition, it’s more costly than other rubberized undercoats and has a short shelf life once opened.
- Fast drying and flexible formula
- Sound deadening properties
- Forms a textured black finish that matches OEM paint
- Resists rust, chipping & weathering
- Comes in 1- and 5-gallon can size options
- Features great sealing, anti-corrosion, and anti-abrasion properties
- Short shell life
- Needs surface preparation before application which can be time-consuming
How to apply an undercoat Paint to your car’s undercarriage at home
After selecting the best undercoat paint for cars, the next step is to apply it on the vehicle’s undercarriage to protect it from rust. However, before you apply the formula, make sure the workspace is clean and has adequate lighting & ventilation.
Also, it’s recommended that you wear a respirator mask and old protective clothing when applying an undercoating for safety reasons. If you’re working outdoors, make sure it is a nice day with low humidity.
And if you’re working indoors, thoroughly clean the room to get rid of dust and other debris that could become trapped in your undercoating.
That said, remove the rust completely by sanding or sandblasting, depending on the extent and area of the rust.
After removing the rust and prepping the undercarriage for coating, rinse it and let it dry to avoid trapping any contaminants on the car’s underside. If possible, use your preferred degreaser to clean the metal surface first before you rinse it.
Next, use a spray gun to apply the selected undercoating to your car’s undercarriage. Here, it’s recommended that you use a disposable spray gun as it becomes very difficult to clean the sprayer once the undercoating hardens.
Apply 2 coats of undercoating to give the undercarriage optimum protection, allowing ample dry time between coats. Finally, let the undercoat cure fully before you drive the car on the road.
Choosing the best undercoat paint for cars goes a long way toward protecting the vehicle’s undercarriage from rust and damage caused by other elements. In addition, they have sound-deadening properties, meaning they’ll reduce the amount of noise coming from the underside and wheel wells.
As a result, you will notice a minor road noise reduction in the cabin, especially at highway speeds after applying this product.