Best Rust Proofing Service: Krown, Rust Check or Corrosion Free?

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Updated February 11, 2021

Rust proofing your vehicle is one of the easiest ways to invest in its longevity and value.

Corrosion can compromise the integrity of your vehicle, from the paint to its safety, and rust proofing will help you reduce repair costs, keep your vehicle looking great, and increase its resale or trade in value down the road.

Before you can choose the best rust proofing solution, it’s important to understand the options available and how they stack up against each other. This guide outlines the strengths and weaknesses of the most common popular options as well as what to watch out for when choosing a service.

ServiceCostApplication TimeWarrantyDrip?
Rust Check$1201 hourAnnually renewable warranties to all cars less than one model year and to qualified cars up to five model years old. Pays for repairs.Occasional dripage
Krown$12045 min to an hourRepair/replace body panels below window line, seams and crevices and floor/rocker panels, up to the current cash value of the vehicle24-48 hours of dripping
Corrosion Free$1501 hourCovers vehicle body structure including the roof and floor pan, up to the current cash value of the vehicle.Drip-free


Krown is a petroleum based rust inhibitor designed to slow down or inhibit corrosion on your vehicle. One of the major benefits of Krown is that it contains no solvents, making it environmentally safe. The solution is non-corrosive, non-flammable, and non-reactive, allowing it to be applied in any weather and actually works as a lubricant on many moving parts.

One of the downsides to Krown is you may experience dripping of the excess product. In order to properly reach into the tight seams of your vehicle, the solution needs to be thin enough. This causes minimal dripping within the first 24-48 hours of application.

Rust Check

Rust Check treats vehicles with a corrosion inhibitor that forms a bonded layer on the surface of the metal. The product then acts as a barrier, preventing water and oxygen molecules to be absorbed by the metal, therefore disabling its ability to rust.

The thin layer is undetectable by the naked eye, and is thin enough to penetrate, lubricate, and protect moving parts, seams, and support braces. Because the layer is non-drying, it will never crack or peel.

Corrosion Free

Corrosion Free is another eco-friendly rust proofing solution that uses their Formula 3000 with CSC 850 to not only inhibit rust, but also to terminate existing rust and corrosion. The formula is designed to eliminate moisture, and is thin enough to penetrate into all of the seams and crevices of your vehicle.

Corrosion Free also protects your vehicle’s vinyl and plastic surfaces, preventing damage from harmful UV rays, so it protects more areas of your car than only the metal parts. Due to the properties in Corrosion Free’s formula, their solution chases down and pushes away moisture, allowing it to creep into wet places you didn’t even know were there.

Tar based undercoating

This type of rust proofing is typically offered by the dealership when purchasing a car. This solution covers over the areas that are susceptible to rust with a tar based product, and can offer a visually appealing look to the underside of your new car.

In terms of functionality, this type of coating is known for some major problems. While great for a short term solution, tar based undercoating can chip or deteriorate. When this happens, moisture creeps underneath the tar layer, becoming trapped and accelerating the corrosion of your vehicle.

Electronic rust inhibitors

Recently, engineers have been developing a technology that uses weak electrical currents sent through the metal of the car. These currents are meant to prevent the electrochemical reaction of rusting, preventing corrosion on your vehicle.

Electronic rust inhibitors vary in price depending on who does the installation. Companies such as Canadian Tire charge as low as $300, while a dealership may charge from $500 to $1000. It’s easy to get caught up in the interesting world of new tech features for vehicles, however the technology is still very new, and its effectiveness is met with mixed reviews from consumers.

What offers the best protection?

There are many things to consider when deciding which option is best for your vehicle, such as type, cost, dripping or non-dripping solutions, as well as the overall effectiveness of the product you choose. Each rust proofing solution is functional in its own way, but some options stand out among the rest.

When deciding which option was the best for us, we looked to a 2006 study done by the Department of Defence Research and Development. This study was done to review corrosion control and prevention on army vehicles, and was prompted due to the rising costs of repair the government was incurring, along with choosing the best solution to increase service life and functionality of the vehicles.

Best overall – Corrosion Free

After an extensive study testing their vehicles in the harshest conditions, Corrosion Free was the clear winner with a 90% effective rating for inhibiting rust. We tend to agree, adding that its clean and transparent application helps it preserve the “factory new” look to your vehicle.

Krown came in second with a 70% effective rating, and Rust Check came in a distant third with a 40% rating. Both Krown and Rust Check are both still considerably viable options when choosing how to rust proof your vehicle, but in terms of overall value and effectiveness, neither stacked up to Corrosion Free.

What about warranties?

When considering the best option for protecting your vehicle, choosing a solution with a great warranty will provide you with the peace of mind knowing you made the right decisions. When reviewing warranties, keep a close eye on how it is affected on both aluminum and steel, the coverage limits, and if the warranty is transferrable to new owners.

We recommend carefully reading through all warranties, but here’s a snapshot of what’s included for the top three rust proofing solutions:

Corrosion Free

Corrosion Free offers a warranty that will repair or replace body panels or structural frame members weakened by corrosion or rust. It also covers roof and floor pan of the vehicle.

Full warranty here

Rust Check

Offers a lifetime, annually renewable warranty to vehicles less than one model year and to qualified vehicles up to three model years old. Their warranty pays for the repairs on rust-thru only, is transferrable, and has no mileage restrictions.

Partial details here


Krown’s warranty will cover all seams and crevices, all floor/rocker panels, and all body panels below the window line. Krown will repair or replace any rust-thru up to the current cash value of the vehicle. Their warranty is transferable at no charge.

Full warranty here

Best – Corrosion Free

Once again, Corrosion Free comes out on top with the best warranty. Corrosion Free is the only warranty that doesn’t require a rust-thru or hole in a panel to cover repairs. Krown and Rust Check also require rust to originate inside the metal, where Corrosion Free’s warranty is valid regardless of where the rust originates.

Things to avoid

Non-oil based products

Options such as undercoating provided by the dealer, or other non-oil based undercoating are old technologies that provide inferior results. These products don’t have the ability to penetrate into the hard to reach seams and crevices where rust is more likely to form. Plus, coatings have been known to crack and chip, causing moisture to trap itself against metal surfaces, accelerating the corrosion process.

Poor application

Choosing a great product means nothing if it isn’t applied properly and by a professional. Even the effectiveness top rated solutions like Corrosion Free can be negated by poor service technicians. Do your research and find highly recommended dealers in your area.

If you can’t find a great dealer for the product you want, it could be worth considering your second or third choice to guarantee it is applied properly and done right the first time.

What to read next

Over to you

Now that you have the information, which solution is best for you? Have you had good or bad experiences with any products or dealers in the past? Let us know by leaving a comment below!

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  1. The article suggest avoiding ‘non oil based’ products. yet, it rates Corrosion Free as most effective rust inhibitor. (Corrosion Free is non oil based). Can anyone clarify why they rate CF as best?

  2. How well the product is applied is by FAR the most important factor. I took my truck to a Krown shop on the advice of a mechanic who was friends with the owner. They had a glass window so you could watch the technicians. Great! But they were busy, and putting multiple vehicles through with more than one technician, assembly line style. I saw that one fender of the truck had been completely missed, and asked that the truck be taken back in and resprayed. The owner came out and said he did that fender himself, so it was done. I said come outside and look at it; it is completely dry. He refused and started yelling that he had done it. I got angry and raised my voice as well, and insisted he come check out to check the truck and respray it. Owner screamed at me to get out of his shop or he would call the cops, with hand on phone. So yeah, research the SHOP applying the rust treatment by looking at all the reviews you can, and don’t take one mechanic’s word for it, or your buddy Joe’s word for it. And you really must check that the product has at least been applied everywhere it needs to go, which is difficult if you can’t watch the techs or if the owner of the shop is…uh…well, I have lots of words that are probably unprintable. Last couple of years I’ve just bought several spray cans of rustproofer, (usually the Formula 3000…it has proven very effective on my trailer hitch left out in the elements all winter), a couple of different types of extension wands to get interior sections, and done the rustproofing myself. If you have an older, mint condition vehicle, and do not want to risk rust, I think this is the only safe way to go.

  3. I have rustproofed or undercoated most of my 30 plus vehicles over my life and highly recommend it. I am however not too thrilled with my Corrosion Free rustproofing that I received this year (my first experience with Corrosion Free). It has been 5 months since the job was done and my car is still dripping from every drain hole along the bottom of my doors, trunk, etc. To me a little dripping or seepage is fine and a good indication of good coverage and a job well done, however this product is sold as “no drip”. So while I can appreciate the thorough job done by the worker I am not all giddy about the product.

  4. I’ve been using Rust Check on my vehicles since 1984 and I’ve never, ever had a rust problem of any kind and some of these vehicles I owned for more than 12 years (southern Ontario). This product does however seem to present problems with rubber components which can stretch and expand over time and I had problems with motor mount bushings and pollution control gaskets on different cars after ~9 years in each case. (I believe this is true of any oil based spray application products.) On balance I would still definitely recommend it.

  5. I have been getting my vehicles treated by Krown for as long as they’ve been around, and I agree it’s more the quality of the application than the product itself. You can develop a product that protects the car like no other, but if it’s applied by an inexperienced or improperly trained technician, or moreover, a technician that is bored, tired, or simply doesn’t give a s**t, your vehicle is not going to be properly protected. I don’t like they way most garages won’t let you watch. They give you some BS about liability and insurance, but in reality, they’re not letting you watch so you don’t see what a lousy job they’re doing. Some shop owners are very diligent about making sure their techs do a proper job, and those are the ones I go back to. I’ve had everything from no plugs installed in the drilled holes, to such a poor job that the inside of 3 out of 4 wheel wells was completely dry after the application. Those are the ones that I don’t patronize again. So again, I feel it doesn’t matter which rustproofing product you try. Properly applied any of them are going to do wonders protecting your investment. Improperly applied, and you’re just throwing your money away, and worse, giving you a false sense that it’s protected when in fact, it’s not.

  6. Ķrown rust proofing is a pure waste of money. Learned from experience. Had a car sprayed so they say.I checked when I got home. They sprayed approximately 2sq.feet behind the gas tank, not a drop anywhere else. The plugs from previous spay were never removed. This is a factual experience.

  7. When I began comparison shopping for a rust-proofing product, for the used, but rust-free vehicle, that I purchased 2 years ago, to protect my investment, I based my final decision to buy the ‘Corrosion Free Complete Rust Cure’ C package, their most expensive option, on the recommendations made on this page. It certainly appeared to be the superior product, as well as the best value for the money. Imagine my surprise now to learn that, because it was applied to a used vehicle, the much vaunted ‘Corrosion Free’ Warranty does not apply! This fact does not appear anywhere in this page’s review of the different rust-proofing products profiled. That’s quite a condition to be blatantly absent! Given my experience, giving ‘Corrosion Free’ your highest recommendation certainly now ‘rings very hollow’. I am now very hesitant to continue using ‘Corrosion Free’, now that I’ve learned the hard way, that they don’t stand behind their product.

  8. My experience with rust proofing has been very different than expected. I have used both krown and rust check and have had very different results than others. I had one truck I used krown and had both rear fenders rust out completely. I now use rust check on my current truck and have had zero rust anywhere on it it. But my experience is probably more related to how it was applied more than what brand it was. In the old days we just oil spray our cars and even that worked well if done correctly. So my opinion is how well the job is done is far more important than what one you use. And don’t be afraid to go take a look at the job they have done and watch them do it.

  9. Great summary, thanks! I’d like to see an additional section discussing whether it’s starting rust proofing on a used vehicle that already has signs of rust. I recently bought a five year old used car. The major items underneath only have light surface rust, but the exhaust has wider spread rust, and some large flakes around the bolted parts. I’m wondering if rust proofing is a waste in a scenario like this.

  10. Been using Krown for 8 years now. Have never kept a vehicle longer than 3 years so can’t speak to it’s worth after that, but no issues in 3 years!

  11. I have been using Krown for over 4 years on my vehicle when I bought it back in 2016. There is no sign of rust at all despite being daily driven in harsh winters. Definitely recommend.

  12. We have used rust check on past vehicles, and i regularly spray suspension with can of rust check when changing snows etc.
    One of the biggest issues we had is where they drill the hole to access the rocker panels – large (1/2 inch or so) hole drilled in the top surface of our rocker panels was the only place we noticed significant rust on our last minivan. Salt/dirt collected around the edge of the plastic plug and that’s where the corrosion started. Perhaps they have become better now at locating holes away from these areas.

  13. My experience: I have used Krown over the last several years on my sedan. Result: rusted rear fender and rusted rocker panels where there was little to no visible corrosion. My understanding was, even if there was some corrosion, the treatments were supposed to stop it from advancing. I knew of someone else who used Rust Check with a car he bough from Quebec (where they use a lot more salt). 10 years of ownership and no advancement in his corrosion. The condition of my car was about the same as his when he bought it but in about four years I have rust penetrations as if my car was never treated. Now, I have extensive body repairs to do no thanks to Krown. Clearly the Krown treatment is not good in comparison to the Rust Check.