PaintSprayerMag is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you.

Best Undercoat Paint 2020 – Reviews & Top Picks

Last Updated on

an undercoat paintIf you’re having problems with rust on your undercarriage, you need to find a way to treat the problem and extend the life of your vehicle. Undercoat paint is a great way to keep rust from spreading and to keep new rust spots from forming.

When you’re shopping online, it’s not always easy to tell if you’re getting a good deal or not, or even if you’re getting a functioning product. That’s why we’ve assembled these reviews of the best undercoat paints of 2020. After reading these reviews, you should be able to find the variety that works best for you and comes that a price you’ll love, too.

We also created a buyer’s guide so that you can learn everything you need to know about undercarriage paint before you buy, so be sure to check that out if you’ve never used this product before.

Comparison Table (updated in 2020):

ModelPriceContainer TypeEditor Rating
POR-15 45404 Rust Preventive
POR-15 45404 Rust Preventive(Best Overall)


Check Price
Tin Can4.95/5
Rusfre RUS-1020F6
Rusfre RUS-1020F6


Check Price
Gallon Jug4.80/5
3M 03584 Professional Grade Rubberized
3M 03584 Professional Grade Rubberized(Best Value)


Check Price
Aerosol Can4.70/5
Penray 4424
Penray 4424


Check Price
Aerosol Can4.40/5
Al’s Liner ALS-UCR1G ALS-UCR
ALS-UCR1G ALS-UCR


Check Price
Tin Can4.25/5

9 Best Undercoat Paints – Reviews:

1. POR-15 Rust Preventive Undercoat Paint – Best Overall

POR-15 45404 Rust Preventive

If you’ve got a rusty piece of equipment or vehicle using POR-15 45404 Rust Preventive is one of the best choices that you could make. Unlike other rust preventatives, you don’t have to scrape off the existing rust before applying, and it does appear that this coating sticks even better to rust than it does to other surfaces. There’s also no need for primer, which speeds up the process and saves you some money in the process, too.

This brand is also very durable and lasts in areas that are high traffic and subject to abuse. The resistance is because this paint stays flexible when it dries, which also makes it nearly shatter-proof. The one downside to this paint is that it stains everything, so you shouldn’t wear anything you like a lot while you work, and you should be careful to put down protection around your work area to avoid stains. Overall, this is the very best rust preventive you can get, and it will give you years, if not decades, of high-quality performance.

Pros
  • No rust removal required
  • Shatter-resistant and flexible
  • Durable
  • Doesn’t require primer
Cons
  • Stains everything

2. Rusfre Undercoat PaintRusfre RUS-1020F6

The Rusfre RUS-1020F6 is good for people who are looking for something cheaper than the first entry on our list but still want a high-quality, durable undercarriage coating. This brand creates a nice, rubberized layer that will hold up well to abuse without chipping or flaking off, due to the inclusion of bound fibers into the mix which helps hold everything together. At first glance, it seems very thick, and you may worry about spraying it on, but heating it in the sun or on a warm engine helps it run more easily.

This material also deadens sounds, so it can be good for older cars that create a lot of road noise. While it’s not a substitute for sound-dampening material, it certainly helps in that regard. There is a pair of problems with this material. It’s even harder to remove than the previous entry on our list, and it also smells far worse. You’ll need to use protective clothing and probably a respirator, too. While it is a pain to apply, it works well, and will be a great choice for people who want a cheaper, but still very effective undercarriage coating.

Pros
  • Chip-resistant bound fibers
  • Rubberized
  • Deadens sounds
Cons
  • Hard to clean up
  • Smells

3. 3M Rubberized Undercoating Paint – Best Value

3M 03584 Professional Grade Rubberized

The 3M 03584 Professional Grade Rubberized undercarriage paint is a good choice for people who only need to treat a small area. It comes in a 16-ounce spray can, which means you don’t have to invest in additional spraying equipment, and it’s just the right size to treat a small area. Since it’s in a can, it’s easy to maneuver, which makes it easy to coat hard-to-reach areas and to treat your undercarriage without putting your vehicle on a lift.

It also comes in a no-run formulation that should mean that you don’t have to wear as much protective equipment when using it relative to other brands and that cleaning up should be easier. One gripe about this brand is that it fades in the sun. If you’re only treating your wheel wells and undercarriage, this won’t matter to you at all, but if you’re like a lot of people who have a habit of using undercarriage paint for other tasks, you’ll probably want to invest in a different brand. You can get this variety for a low price, and its small amount and easy application make it perfect for people who need to treat a small area.

Pros
  • Small form factor
  • Easy to apply
  • Cheap
  • No-run formula
Cons
  • Fades in the sun

4. Penray Rubberized Undercoat

Penray 4424

If you’re looking for thermal protection from extreme heat and cold, the Penray 4424 rubberized undercoat may be one you take a look at. Interestingly, this product claims to also be good for minor roof and gutter repairs. We didn’t test it in that capacity, but it performed admirably on the vehicles we tested it on, although not well enough to earn the top spot on this list.

What sort of value does this spray provide? To start, it’s very fast drying. Thanks to the waterproof formula, it’s also a great protectant against rust and corrosion. This Penray spray helps to reduce the impact of road noise inside the cabin, though achieving this required quite a few coats. In fact, multiple coats were required to achieve most of the effects we were looking for. We had achieved very few of the desired effects after applying a single coat, and the poor coverage left a lot to be desired.

Pros
  • Cost-effective
  • Quick-drying
  • Waterproof
  • Reduces road noise
Cons
  • Not very effective as a single coat
  • Poor coverage

5. Al’s Liner Rubberized Undercoating

Al Liner ALS-UCR1G ALS-UCR

Al’s Liner is only available in a paint-on formula, and it tends to be extremely messy in our experience. That said, it was also quite effective. However, we would have preferred a spray-on version that makes it easier to get an even coating. This formula doesn’t crack or dry out. After applying it, we experienced no peeling. While it displayed some sound deadening properties, they didn’t live up to our expectations.

The very short drying time surpassed our expectations. Al’s Liner claims their product is paintable in only 30 minutes, and in our experience, this is pretty close to true. Ours wasn’t fully dry that fast and we didn’t want to chance it, but an hour would be a pretty safe statement. Of course, this is going to be dependent on the thickness of your application. You can get this coating in quantities up to a gallon which makes it easier to complete a large job, but expect to pay a premium price for this product.

Pros
  • Quick-dry formula
  • Doesn’t crack, peel, or dry out
  • Sound deadening
Cons
  • Expensive
  • Paint-on formula only
  • Messy

6. Rust-Oleum Rubberized Undercoating

Rust-Oleum 248656

If price is your main concern, you’re probably going to be attracted to the Rust-Oleum 248656 professional rubberized undercoating when you first see it. It is the most affordable option that we’ve reviewed. But don’t let that be the only point you judge this coating on, because overall, it’s a pretty capable coating that’s got decent value considering its very low price.

If you’re looking for a spray that reduces road-noise, then this undercoating can help you out. It also doesn’t drip or run, and it offers excellent protection from corrosion, water, salt, and chemicals. That said, expect to spend some serious time on prep work. If you don’t get your surfaces absolutely bare and clean, this undercoating will not stick. If you get it to stick, expect some serious drying time before you can paint. In our experience, 48-72 hours were necessary. This is far worse than most of the competing brand’s offerings.

Pros
  • Doesn’t drip or run
  • Very affordable
  • Deadens sound and road noise
Cons
  • 48-72-hour total drying time
  • Requires proper prep
  • Won’t stick if surface isn’t prepped perfectly

7. POR-15 Black Rubberized Undercoating

POR-15 49308

This rubberized undercoating from POR-15 offers most of the standard properties you’d want in a spray-on undercoating product. It’s a great moisture barrier, so it protects against corrosion from the elements. It’s also a pretty effective sound barrier, though we found that achieving this effect requires several coats.

So why doesn’t the POR-15 49308 spray rank higher on this list? For starters, we think it’s very overpriced. While it is a pretty effective spray, it’s several times the cost of other sprays that are just as effective. Worse, we experienced continuous problems with the spray nozzle clogging. We had to stop our work repeatedly just to unclog it. After looking into it, this seems to be a very common issue with this spray. The final drawback was the very intense fumes associated with it. While most of these sprays did have some fumes or chemical odors present, none of them exhibited them to the extent that this one did.

Pros
  • Thermal and moisture barrier
  • Sound barrier
Cons
  • Very expensive
  • Terrible spray nozzle always clogs
  • Strong chemical fumes

8. Dupli-Color Paintable Rubberized Undercoat

Dupli-Color EUC101A00

The Dupli-Color EUC101A00 rubberized undercoating is a very affordable spray-on coating, but it doesn’t live up to its claims. We’d be willing to pay a bit more for a product that works as advertised. In its defense, it sprayed on well and gave an even coating that we thought looked good.

Despite being advertised as quick-drying, for us, the Dupli-Color spray took several days to fully cure. If you’re trying to get your vehicle back on the road, then this length of waiting time may be more than you’re willing or able to park your wheels for. It doesn’t offer heat protection, so you won’t want to use this product for coating your firewall. It does slightly aid in reducing road noise, but not as well as other products in the same price range. Overall, it wasn’t our favorite choice, though it did mostly do what it claimed.

Pros
  • Very affordable
  • Goes on well
Cons
  • No heat protectant
  • Takes days to fully dry
  • Doesn’t stick well, flakes off

9. Permatex 80072 Undercoating

Permatex 80072

While it’s not the most economically priced product on this list, the Permatex 80072 coating is affordable. It claims to sound-proof, protect, and insulate. In our experience, it does these to some degree, but not at all how the can makes you believe.

The claim of not sagging or dripping is completely bogus since ours was running and dripping all over the place no matter what we did. When spraying, it was clumping up and achieving an even coat was near-impossible for us. Worse yet, it didn’t even want to stick to some surfaces we tried to spray. When it did stick, it dried to a coating that seemed like it would provide some protection, though it didn’t provide a finish that you would want visible. Overall, this is not a product that we would recommend, though it’s not the worst on the market.

Pros
  • Affordable
Cons
  • Doesn’t live up to advertising claims
  • Terrible spray is clumpy and uneven
  • Lots of drips and runs
  • Didn’t stick to all surfaces

Buyer’s Guide

Whether you’ve never bought undercoat paint before, or you’re an old hand looking for a refresher course, there’s something in this buyer’s guide for you. We’ve packed it full of good general information about the thinking that went into our reviews, so if you want to understand why things got the ratings that they did, this is a good place to start. We’ve also added a ton of good information about undercoat paint so that you can learn about its features and potential applications before you buy it.

Severity of rust

One of the first things you need to consider when shopping for undercoat paint is the severity of your rusting problem. The problem’s severity is going to change how you tackle the issue. If you have a bit of rusting in a spot or two, you may just need to coat the undercarriage in those spots to keep it from spreading. In these instances, it makes sense to buy a spray can of paint. That way, you’ll be able to get to those spots without having to jack up your car, and you won’t have too much excess paint left over.

However, if the damage is more extensive, then you’re probably going to want to coat the entire thing, which means that using a spray can-based undercoat paint is inefficient. You’ll end up buying a ton of cans, which will be expensive, slow, and environmentally-wasteful. Instead, you should be buying undercarriage paint by the gallon, and using good spraying equipment to quickly and efficiently coat the underside of your car. You’ll have to raise it up to do this, but the added speed and efficiency will make it more than worth the effort.

If the rusting is incredibly severe, for instance, if the entire surface is cracked, pitted, and completely covered in rust, you don’t want to use traditional undercarriage paint. In that situation, you’d be better off with a rust converter, which transforms rust into a ceramic coating that protects the remaining metal underneath. If you use undercarriage paint on rust that severe, you’re just covering up the problem. The rust will continue to spread underneath the coat and could affect the structural integrity of the metal in question.

Ease of Application

The ease of application also matters when you’re working with undercoat paint. One of the nicer things about spray can-based undercoat paints is that you don’t have to own additional spraying equipment to apply the paint. These cans are also small enough that you can easily get to most places underneath your vehicle to apply the coating without raising up the vehicle. You also generally don’t have to wear as much protective coating, nor do you always need a respirator when working with these kinds of undercoat paint.

If you’re going to use a sprayer to apply undercoat paint, you’re going to have to take more precautions. Sure, application is going to be much easier, faster, and you can generally use better products when you use a sprayer.

The downside is that the sprayer tends to cause the coating to go everywhere. That includes the garage floor if you’re working inside, where the coating will probably become permanent. Likewise, if it gets on your clothes, which it probably will, it’s not going to come off, no matter how many times you wash them. While you’ll eventually be able to get it off your skin, its reminiscent of superglue in that it can be nearly impossible to remove, and in some circumstances, you’ll just have to wait it out.

That’s why you should always wear full protective suits, clothes you don’t like and use a respirator when you work with a sprayer because you don’t want this stuff on you or in your lungs, either.

Which undercoat paint is right for you?

While there are a lot of high-quality undercoat paints on the market today, there’s no one variety that’s going to be the right solution for all people. While you could just look for the cheapest brand out there, that’s not the best way of ensuring that you get the best value or the most bang for your buck.

Instead, you first need to think about what problems you have, and what would be the best way of solving them. Once you know that you’ll have a rough idea of what features you need from your undercoat paint, you can eliminate a lot of options from contention, and that means that no matter how much you spend, you’re getting what you need.

Once you have a short list, you can find the variety that best meets your budget, has all the features you need but doesn’t have extras you won’t use that drive up the price. Now that you’ve done that, the paint you buy will be the best possible value and should give you a great rust-preventing experience.

Conclusion

The POR-15 45404 Rust Preventive is our top choice, featuring great durability, even without primer or rust removal. The Rusfre RUS-1020F6 is a cheaper choice that works nearly as well but is far harder to clean up after. The 3M 03584 Professional Grade Rubberized undercarriage paint comes in a small, inexpensive spray can that is good for people who only want to treat a small area. The Penray Companies 4424 rubberized undercoat doesn’t function as well as other entries on our list, requiring multiple coats and scraping to work.

Hopefully, our reviews and our buyer’s guide have helped you see what you should be looking for when shopping for undercoat paint. You should now be able to use this information to find the variety that is right for you.

Related Guides: