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Best Undercoatings of 2021: Rust Proof Your Car or Truck

Undercoating is not often thought of when automotive detailing and car care are discussed. It is more of a car care product than a detailing product, but it should be discussed more, especially given its potentially vehicle-saving features. Its main job is to protect against corrosion by creating a shield on the bottom of your vehicle.

Although it is not as common anymore, rust used to be a huge issue for most vehicles on the road. A harsh climate, bad weather, road grime, road treatment materials, and normal wear and tear can all take quite a toll on the undercarriage of a vehicle. All of these things can break down vehicle components like the chassis, bodywork, and even the engine over time, causing some major issues.

The Best Undercoating Products

Most modern vehicles are made with more corrosion-resistant materials than vehicles of the past, and some even come with a factory undercoating – at least, many dealerships provide an option for this at the time of purchase at an extra cost. But, you can just as easily give yourself some peace of mind and apply an affordable undercoating yourself.

1. CRC Industries Rubberized Coating

CRC Industries provides a full line of protectants, degreasers, and sealants for various applications, including vehicles and boats. Their focus on these types of products means that you can trust their product to get the job done and provide as much protection as possible.

Their rubberized coating provides an even, tough coating on the underside of your vehicle that is flexible for added protection against scratching and abrasion. It is also quick-drying so that you will not have to wait around too for the product to fully cure.

In addition to protecting your vehicle's undercarriage, CRC’s formula provides additional sound deadening so that your drive can be quieter and more comfortable. Even though the underside of a vehicle is rarely seen, it dries smooth to be even less noticeable than it already is.

2. CorrosionX Corrosion Technologies Heavy Duty

CorrosionX Heavy Duty aerosol spray is a do-it-all product that has stellar ratings for its wide range of abilities and uses. Its application seals out moisture from the surface, including from pressure washing and submersion in saltwater.

Similar to CRC’s coating, CorrosionX Heavy Duty does not dry but forms a flexible yet tough rubberized finish on surfaces that self-heals when scratched. This prevents both cracking and drying out, allowing it to last for longer than many other corrosion inhibitors.

Unlike many other undercoating products, CorrosionX is safe for use with electronic applications, and its heavy-duty formula allows it to be effective even in tough environments like marine and agriculture. Furthermore, it can stop corrosion by penetrating the corroded surface and removing moisture from the area.

3. Fluid Film Lubricant/Corrosion Inhibitor

As its name implies, Fluid Film Lubricant/Corrosion Inhibitor is versatile, able to be used as both undercarriage protectant and lubrication product. It stops rust from spreading on contact and has penetrating capability that allows it to last for up to one year.

Its lanolin-based makeup gives it a soft, scratch-proof finish that will self-heal if damaged. This also allows it not to chip or crack over time due to exposure to the elements. Unlike many other products, Fluid Film’s product can be used on multiple types of metals, paint, or plastic.

Because of its high flash point and anti-conductive properties, it is also useful for corrosion prevention on battery terminals, hinges, and even chrome. If used as an undercoating, Fluid Film says that only a gallon of product needs to be used on most average-sized vehicles.

4. Rusfre Automotive Spray-On Rubberized Undercoating

Rusfre’s Automotive Spray-On Rubberized Undercoating comes in a huge one-gallon container which ultimately saves a buck or two but also allows for a “one-stop” shopping experience without having to purchase multiple containers of product.

It is designed to work with Rusfre’s BBB spray gun which is sold separately, but buyers are treated to an even, spray-on coating that is scratch, chip, and crack-resistant. Because it does not harden, it also functions as a sound deadening shield for a more comfortable driving experience.

It is chemically formulated with bound fibers for better clinging to the underside of vehicles and rust inhibitors to stop and prevent corrosion. The company does warn that the product should only be used for black surfaces.

5. 3M Professional Grade Rubberized Undercoating

3M is a well-known company that provides a variety of common household and industrial products, but they are lesser-known for their automotive applications. Their Professional Grade Rubberized Coating will make buyers aware that their automotive products are top-notch.

This coating can be used for multiple applications including cars, trucks, and recreation vehicles. Its professional-grade asphalt-based formula provides a textured coating that protects against rust, scratching, and abrasion. Additionally, it dampens road noise for a comfortable drive.

Its aerosol dispenser provides ease of application and prevents dripping after properly applied. A relatively low cost also means that this superior product is easily accessible to everyone from the average buyer to the professional. 

While the last entry on the list may not be as flexible as the previously mentioned undercoating sprays, you can rest assured that the quality is on a very high level.

Why Use Aftermarket Undercoating

undercoating spray

As we mentioned before, many vehicles either come from the factory with some type of undercoating, dealer-added undercoating packages are often available upon purchase of a vehicle, and modern vehicle building materials are either corrosion-resistant or are infused with anti-rusting materials. This brings up the question of why undercoating is needed, even if it is fairly inexpensive.

There are three main reasons that undercoating should be considered, despite the advantages modern vehicles possess. 

Not All Vehicles are “Modern”

Everybody’s definition of what a modern vehicle is might be a little different. The average age of a vehicle on the road today is over ten years old. There are still plenty of vehicles on the road that do not have the latest rust-proofing technology and was not built with the absolute latest building materials. These types of vehicles can benefit from aftermarket undercoating.

Better Does Not Mean Perfect

Even if you have a thoroughly modern vehicle, all the best of everything does not guarantee that each part and piece will always hold up to the elements. For the newest of vehicles, choosing to apply an undercoating may be more of a safety blanket than a necessity, but it still may go farther than you think to ultimately prevent corrosion damage.

Wear and Tear Still Exist

The outdoors is not a friendly place. Even the cleanest of roads have its own form of debris somewhere. In climates where seasons are very distinguishable, road salt, a very potent corrosive material, can wreak havoc on any vehicle, no matter how new it is. Extra protection is never necessarily a bad thing to protect from any outside elements or materials, especially in harsher climates.

How Does Undercoating Work?

An undercoating works very much like wax does after you detail your vehicle. The difference is that undercoating is usually rubberized to provide a soft or firm yet giving a protective layer over the entire underside of a vehicle. This coating is usually soft to prevent chipping that can come from a typical enamel, and many products are scratch-resistant or "self-healing."

Also like wax, undercoating needs a clean surface on which to stick so that the product can bond with the surface. This provides a protective seal against contaminants and moisture which is ultimately what causes rust and corrosion. Some products can even expand and prevent rust and corrosion from spreading farther to other surfaces.

Types of Undercoating

There are four main types of undercoating, all of which provide varying degrees of application ease and results.

Spray-On

Spray-on coatings are the most common type of undercoating. They are self-explanatory and easy to apply, and they are effective for their cost. The main reason these do not work as well as many hope is because they are often not applied correctly and need to be reapplied every one or two years.

Lanolin Wax

Lanoline wax is interesting in that it can be used as both a rust inhibitor and as a lubricant. When it is used as an undercoating, it expands to fill holes, similar to spray-on insulation. The main downfall of lanolin wax is that it can take a long time to fully cure.

Dripless Oil Spray

Dripless oil spray is more like an actual wax coating than a rubberized coating. It hardens more than typical spray-on coatings and can last longer, but it sometimes requires drilling into certain points on the treated surface to ensure that all the nooks, crannies, and surfaces are protected.

Electricity

This is a strange one. The theory is that electrical current continuously circulating through a vehicle frame will prevent the chemical reaction needed for corrosion to occur. This is relatively unproven, but it is used and is a permanent anti-rust and anti-corrosion solution that does not require re-application of protective material.

Important Application and Safety Warnings in Regards to Undercoating Products

Most spray-on undercoating products are highly flammable. This is usually not a big deal when it comes to practical use, but it could be a factor if being applied to hot vehicle components or comes into contact with parts like the exhaust or other components; Most bottles feature multiple prominent warnings to users.

Read the instructions and warnings. Our advice usually only consists of recommending reading the instructions for any product; This is still the case, but undercoating tends to be very toxic. It is important to read all the safety instructions for any undercoating product you buy, not only to get your money’s worth during application but also a more fatal problem.

Final Thoughts

Undercoating is a lesser-known, less understood product in the vehicle care segment. It can protect any vehicle, no matter how new it is, and spray-on undercoating products can usually be applied easily and effectively if the instructions are followed.

There are several different types of undercoatings to suit different tastes, all of which provide different advantages and disadvantages. It is always important to consult an expert if you have any questions, and it is important to read the instructions on any undercoating product you decide to buy.

Richard Reed
I've been a General Manager of a moving company and I've also been a Professional Mover for over 30 years. I've driven flat beds, reefers, dropdecks, moving vans, heavy machinery, etc. In my time as a Mover I've driven over 1,000,000 safe miles. My days of moving and driving truck are past me but The Vehicle Lab allows me to share the knowledge I've gained over the past 40 years.
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