Any time you take on a painting project, it can be a big undertaking, and the undercoat paint you choose can make or break the time you invest in the project.
No matter what surface is being painted, without a good undercoat, it won’t come out the way you want it to. Your home deserves the best, and the best comes from underneath.
Before deciding on what color you’d like to paint, it is vital to pick which undercoat you need to use. Remember the important thing to think about when choosing the under coat paint you’d like to use – pick something appropriate for the surfaces you’re painting, and the desired outcome of the project.
Consider the size of the surface that you’re painting and whether you want to use a spray application product or a canned product. Also consider what kind of surface you’d like to paint on top of.
Best Undercoat Paint - Comparison Guide
3M 03584 Professional Grade Rubberized
Rust-Oleum Automotive 254864
POR-15 45404 Semi Gloss Black Rust Preventive Paint
1 qrt or 1 pint
Rust-Oleum 248656 Automotive 15-Ounce Spray
Automotive Spray-On Rubberized Material
Dynatron 544 Dyna-Pro Paintable Rubberized Can
1 or 5 gallon
Penray 4424 Rubberized Undercoat
TRANSTAR (4363-F) Quick Dry Rubberized
3M 08881 Undercoating
Evercoat 1348 Low VOC Premium Rubberized
Advantages and Disadvantages of Rustproofing your Vehicle
To make the car stand up against the wear and tear of the elements, undercoating tends to be a good idea.
This is especially true when living in areas such as Hawaii or South Dakota.
Living in close proximity to the ocean means your car is subjected to salt air. Objects that are in contact with salt water tend to become rusted faster than others.
That’s because salt creates a reaction that begins the oxidizing process. When a car becomes dented or damage, it creates openings in the paint where rust can easily occur.
This is the same concept for people who live near a lot of snow. They will be traveling on roads where salt is used to melt ice. This salt will also cause corrosion to a vehicle and therefore should be protected. Another benefit is that the undercoating can be a sound dampener making it quieter on the road.
There are some drawbacks to consider before undercoating your vehicle. The first is the cost. Car dealerships can charge a good amount of money to apply an undercoat to a car. Another downside is the additional weight the undercoating can apply to a vehicle. This can affect a car’s fuel efficiency.
Different Types of Undercoating
When looking to apply an undercoating, you will notice several types available.
Water and Paraffin-Based
Water-based tend to be the most popular for DIY projects. They are found in automotive parts stores generally in an aerosol can. They are thin set and have fast drying times. The downside to this type is that they often need to be repeated at a later date.
The paraffin-based coating contains a wax to make it slightly stronger than a typical water-based undercoating. These are available as a spray or paint-on formulas. They should be replaced once a year.
Petroleum and Rubber-Based
A petroleum-based undercoating contains oil and will deflect road salts and debris. It also repels water better than a paraffin-based version. These formulas are generally only available through a professional provider or applied when purchasing a vehicle. You will need to replace this once per year as well.
A rubber-based coating is the second strongest available. It is designed for rough terrains due to the flexibility in the undercarriage. They are available as a spray or paint-on application. It can also be purchased as an option when buying a new vehicle.
An asphalt-based undercoating is the strongest you can purchase. It is meant for all-terrain or military vehicles. It lasts the longest and is the ideal option for a vehicle that sees heavy road use.
Polyurethane, or “poly” for short, is a self-sealing undercoating material. When applied, it will get into cracks, nooks and corners, sealing the metal, bonding over rusted or oxidized areas, and pushing out moisture, sand and salt.
You can get poly undercoating in a pail, but most applications come in a ready-tube or coanister for use in an application gun.
Benefits of Undercoating
Undercoating has several benefits when applied correctly. Below I will cover these benefits to help you decide if an undercoating is the right choice for you.
Car repairs are costly. Bodywork can easily exceed the value of the car, and an undercoating will help you save on these costs. By protecting the underside of the car, you help prevent the rust and damage caused by driving (or the environment), reducing the need for costly repairs.
Reduce Road Noise
Because undercoating is a rubberized coat that seals almost the entire undercarriage of your vehicle, you also get added dampening from road noise. This will increase the road noise suppression inside the cab of your car or truck, making your vehicle quieter on the road.
Extra Layer Of Protection
Rust, mold, oxidation, mildew, salt build-up, grime; all of these things happen to our cars every time we take them out on the road. A solid application of undercoating will help prevent all of these things as well as helping the car wash better when the undercarriage is cleaned.
Considerations When Buying Undercoat Paint
Before you head out and buy a bucket of undercoating, there are a few things you should consider. Let’s take a look at those considerations now.
How much undercoating do you need? It is easy to buy too much undercoat, and if you spend the money, it will most likely go to waste. The best prevention here is to determine how much coverage your car or truck will need and buy accordingly.
You may find special offers on undercoating and want to buy now to apply later. This is possible. However, most of the undercoating materials do have a shelf life. If you don’t plan to use the material within a few months of purchase, wait to buy.
It is also easy to want to buy enough material to do multiple cars. However, it isn’t always practical to do all of your vehicles at the same time. If your project spans over some time, you may want to buy only what you need when you need it.
What is your undercoat made of? While it may not seem like much of a concern, different areas of the country will do better with different types of undercoat. For example, those that live near the coast are more susceptible to salt and sand corrosion. Meanwhile, in the Midwest, road grime, oil, and physical damage protection are more viable.
Different materials will have different functionalities. Some undercoats are sandable and paintable; others are not. You may also want to find an undercoat that has a fast drying time so you can get the job done and begin using your car again right away. If you are buying the undercoat for the road noise reduction qualities, make sure you pick one that specializes in noise reduction, as not all of them can.
You will also want an undercoat that can fill in by itself. Otherwise, you will find that the application takes too long and isn’t even. Self-leveling undercoats and self-sealing materials will make the job smoother and the result more professional.
10 Best Undercoat Paints Reviewed
Some choices are better than others and this list should help you decipher the good options for your project.
To help you decide which of the number of undercoat options to choose from, I’ve compiled a list of the best under coat paint to help you get started on your paint project.
1. 3M 03584 Professional Grade Rubberized Undercoating - Best Choice For Cars & Trucks
This is my number 1 option to use on vehicles and other items made of similar metallic materials. The black undercoating provides a good base to paint on top of, and it provides a perfectly smooth rubberized surface on which to put the next coat of paint.
The easy spray can, may not be best for large surfaces, but it works well when patching up small areas on a vehicle. Special chemicals within this product also help prevent corrosion, so that the coat of paint you add on stays on!
2. Rust Oleum Automotive 254864
- Quantity of (12) cans: 15 OZ, Black...
- An Easy To Use, Black Protective Coating
- Protects Metal Surfaces From Corrosion &...
- Trusted Rust Preventive Formula Provides A...
Rust Oleum has produced this fantastic, professional grade undercoat paint that comes in a 32-ounce can, which makes it great for larger projects! Perfect for all types of vehicles, and the unique formula prevents against rust.
The rubberized coating that this product leaves behind also has a special feature that helps to reduce sound that comes from clinking and clanking vehicles on the road.
The final benefit of this product over this is it’s quick dry quality. By drying quickly, it allows you to get that first coat on, and move on to the next within a very short amount of time. DIY quick time!
3. POR-15 45404 Semi-Gloss Black Rust Preventive Paint
POR-15 makes this high-tech and high-performance rust-preventive coating that is specifically designed for applying to any rusted or seasoned metal surface. By protecting the metal from further exposure to moisture, this formula can effectively prevent future rusting.
Don’t just use this product as an undercoating to your vehicle! It can be used on most any metal surface as a protective paint against the elements. In addition, it is sold in 1-pint or 1-quart containers, so you can purchase just what you need to get the job done.
4. Rust-Oleum 248656 Automotive 15-Ounce Undercoating Spray
- Perfect for use on bare or primed metal...
- Professional-grade formula provides superior...
- Dries to the touch in 1 hour and covers up to...
- Undercoating helps deaden sound and reduce...
The Rust-Oleum brand does it yet again with this professional grade and paintable undercoating spray. It deadens sound and road noise as well as provides superior corrosion and moisture resistance.
This 15-ounce spray offers corrosive protection from water, salt and other chemicals. You can use it on cars, trucks, recreational vehicles and trailers for a superior protection. It dries quickly into a professional-grade rubberized material.
This low-cost spray goes on easily and would be simple enough that even a beginner could use it.
5. Rusfre Automotive Spray-On Rubberized Undercoating Material
This rubberized, chemically formulated material is an effective rust preventive product. The formula contains bound fibers used for creating a superior bond. This bond prevents cracking, peeling and chipping.
It can be sprayed on for an even finish or used with a brush if you prefer. It covers completely and also deadens sound. There is no asbestos in this formula.
This automotive material also seems to work well in the tailgate, doors and rockers. In fact, you can reduce it about 20-percent and help it to flow into seams for complete protection. The price for a gallon of this undercoating material is very reasonable and well worth the money.
6. Dynatron 544 Dyna-Pro Paintable Rubberized Undercoating Can
- Flexible rubberized coating resists...
- Fully paintable and texturized to match OEM...
- Forms electromechanical barrier against rust,...
- Like applying a layer of rubber to areas most...
Backed by 3M, this Dynatron Dyna-Pro Paintable Rubberized Undercoating provides a durable barrier against the elements. It effectively protects against weather, salt spray, rust and chipping.
The fast-drying and flexible coating combines either an easy brush or spray-on application so you can do whatever is easiest. The superior sealing and corrosion resistance formula is a great option when looking to protect your vehicle from rust damage.
In addition, this is going to help deaden sounds and road noises as well. It can be purchased in 1 or 5-gallon containers so you can complete any sized job.
7. Penray 4424 Rubberized Undercoat
- Quick Drying, Black, Rubberized, Waterproof...
- Protects Surfaces from Rust, Corrosion,...
- May Be Painted Over with NO Bleed-Through
- Automotive Applications Include:...
This quick-drying rubberized undercoat is waterproof and can also be painted over. It effectively protects the surface from rust, extreme weather, dust, fumes, road salt and corrosion.
When painting over this Penray formula, you won’t have to worry about bleed-through. Use this on all automotive applications including the undercarriage, wheel wells and frame. You can also expect a reduction in road noise when using this product.
This isn’t just for automotive use. It is also ideal for minor roof repairs, downspouts, gutters and works on your foundations. This product comes in an easy-to-use spray for simple application.
8. TRANSTAR (4363-F) Quick Dry Rubberized Undercoating
While this Transtar product isn’t overflowing in customer reviews yet, I think it will be soon. This quick-drying protective automotive coating is easy to use, even for a beginner. It will resist abrasion while preventing rust. It also is effective at sealing out dust and moisture. On top of that, it reduces road noise.
The Transtar spray is also great for other applications like recreational vehicles and trailers. I love that it is fully paintable, but I am not thrilled with the price.
9. 3M 08881 Undercoating
- Provides a tough barrier and protects metal...
- An aerosol undercoating with smooth texture...
- Multi-purpose undercoating may be applied to...
- Hides welding marks and other repairs
This aerosol undercoat paint creates a rubberized surface on which to apply the next layer of paint. It is an excellent option when you’re concerned about potential rusting of the surface you’re painting.
This product is less suitable for the outside surface of a vehicle, but geared more towards the undercarriage of vehicles. It is also a good option if you’re repainting/recoating the fenders and bumpers of the car as well.
Once again, the spray can provides an easy-spray application for smaller surfaces and DIY projects.
10. Evercoat 1348 Low VOC Premium Rubberized Undercoating
- Premium rubberized undercoating
- Adheres to bare metal or previously painted...
- Creates a tough, flexible, textured surface
- Non-asphaltic, can be used on rocker panels,...
The Evercoat under coat paint is a great option if your DIY project is a redo! This option works on surfaces that have already been painted. This product creates a rough, grip-able surface for you to add your next coat of paint.
It’s a great option to use on the undercarriage, bumpers and underbodies of cars or similar surfaces.
This option is described as a ‘premium’ option, because of it’s longevity. You can guarantee that you’ll only have to make this decision one time if you choose this option, because the undercoat paint is reliable, and will allow the next coat to stick firmly to the surface you’re painting.
Ways of Undercoating Your Truck or Car
There are several different ways to undercoat your car or truck.
A spray undercoating adheres to your vulnerable parts of the undercarriage. These seal out the environment, chemicals and abrasive elements from affecting the undercarriage. They come in an easy-to-use spray formulation and are also helpful to deaden road noises. You’ll find superior moisture resistance without having to do a lot of work.
This also protects the metal surfaces from moisture and corrosion, plus offers a weather-resistance scratch-resistant formula. The beautiful thing about a rubberized undercoating is that road debris can’t stick to it. In addition, it’s easy to customize because you can paint over it. You can often spray this formula on or use a brush.
This formula not only prevents rust, but it’s also available in large sizes. This is nice if you have a lot of area to cover. Another benefit of undercoating paint is that it will dry quickly. This allows you the chance to get your first coat on and move on to the second without much delay.
3M is a science company that uses 46 different technology platforms to create innovative products. They are located in St. Paul, Minnesota and their products have been used by hundreds of millions of people around the world. They have reached $30 billion in sales and employs more than 90,000 employees worldwide.
Rust-Oleum specializes in manufacturing coatings and paints for both industrial and home use. It’s been around since 1921 when Robert Fergusson, a sea captain at the time, noticed that the raw fish oil stopped his metal decks from corroding any further.
That’s when he decided to implement whale oil into a protective product. While they no longer use whale oil, you can trust them to protect your precious items as well.
Quick Guide - How To Apply Undercoat Paint
Follow these simple steps to quickly apply undercoat paint:
- 1Clean the underbody with a degreaser.
- 2Remove any rust with a grinder.
- 3Sand any remaining rust. The grit should be at least 220 or larger.
- 4Wipe away any remaining dust.
- 5Paint and prime the underbody of the vehicle. Allow this to dry completely before moving on.
- 6Apply undercoating liberally to the underbody. Any part of the car that will be exposed to the road should be covered. Allow the first coat to dry for at least an hour.
- 7Apply a second coating.
- 8This should be allowed to dry overnight before driving again.
If you need to remove the undercoating at any time, it is a simple process. Simply spray the undercoating with a recommended paint remover. You could use products such as paint stripper, aircraft stripper or solvents.
Sometimes, just a simple heat gun will work as well. Once the undercoating is softened, take your scraper and remove it carefully.
Frequently Asked Questions
Do I have to remove the wheels when undercoating the underbody?
It isn’t a law that you need to remove your wheels. However, it is highly recommended. Overspray is bound to happen, and the undercoat isn’t something you want on your wheels. It can throw off the balance and make your car wobble when driving. It is always best to remove as much as possible before painting, including your wheels.
What should I use to clean my vehicle before applying an undercoat?
You can use a garden hose with a nozzle if you prefer. Power washers work well, too. If you want a fast method, take your car to a drive-through car wash and pay for the undercarriage clean. This won’t get it clean enough for the undercoat, but it will help you remove the big stuff. Once that is done, you will need to wash the underside with a degreaser to remove oils and grease before applying the undercoat.
How often should I give my vehicle a new undercoat?
If done correctly, you will only need to undercoat your vehicle once. If there is excessive damage to the undercoat after some time (perhaps you ran a curb or hit a large pothole), a touch-up coating may be warranted.
Any kind of DIY project is a big undertaking, and one you only want to do once. Whether it’s a small surface on a car, or something that seems unimportant, choosing the right under coat paint is the one of the most important parts of the process.
So that you only need to go through this process once, make sure you pick the right one. There’s no point in doing a DIY project that you’ll have to DIY once, twice, three times or four. This list I’ve compiled is an excellent guide in making this important decision.
Good luck with your project, I hope this has helped you pick out your starting point!
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