Best rust inhibitor | How to prevent corrosion on your motorcycle

Properly clean your bike and prep it for winter and it’ll survive the salt that can lead to corrosion and rust damage. Products like ACF-50, XCP Rust Blocker, Scottoiler FS 365 and TechCote ACS TC200 are popular among bikers when it comes to keeping rust at bay, but how good are they really? And once you’ve chosen one, what’s the best way to apply them?

This test is slower than a lab salt spray test, but it’s designed to reflect a bike being ridden morning and evening, with a wash off at the weekend

What is the best motorcycle rust inhibitor?

In order to test how well the most popular corrosion protectants stop your bike from rusting, I cut multiple fresh steel plates to size and folded them in the middle to 90°, to provide vertical and horizontal surfaces.

These plates were thoroughly cleaned with 99.9% pure isopropyl alcohol, dried, then coated with each product as per the manufacturer’s instructions before being left for 24 hours.

The plates were suspended in a crate kept indoors with a reasonably regulated temperature and sprayed twice a day with a 5% road-salt solution.

Every weekend the plates were thoroughly hosed off with clean water.

If you watch the videos in this article you’ll see the timelapses I shot of the entire testing, which give you an even better idea of what protection is offered.

The graph above clearly shows the results of my testing, and while these performance figures are based on separate tests as new products were released, ACF-50, XCP Rust Blocker, Tech-Cote ACS TC200 and WD-40 Original were all included in the repeats as a control reference, and the results were almost identical.

ACF-50, XCP Rust Blocker and XCP Clear Coat are all available in aerosol can form or as a bottle, which can be applied with a compressor and paint gun, allowing it to mist up into hard to reach areas. Both application methods were tested, as well as XCP Rust Blocker Clear Coat in a spray bottle as it’s a lighter product that can be applied easily this way. ACF-50 is also available in a pump bottle, but this wasn’t tested as it delivers a stream that’s hard to apply to a bike.

The test was stopped after seven months, but at this point TechCote ACS TC200 was at 80% rust coverage, while XCP Rust Blocker (in aerosol can form) was at 50%.

Scottoiler FS365 is the unusual one in this test as it’s intended to be a quick-wash and corrosion inhibitor combined – it’s water-based and meant for people riding every day who’ll give their bike a quick spray when they get home. I tested it using two methods – one was to spray it on once then leave it, the other was to reapply it once a day, in the evening after the second spray with salt solution. Using it this way, corrosion covered 50% of the steel plate after 18 weeks, then stayed at this level until the test was stopped.

These products were all selected based on their claims, or after recommendation by the Bennetts Facebook community, but it’s obvious that those designed specifically as corrosion protectants tended to fare the best in this corrosion test; GT85, for instance, isn’t sold as a corrosion inhibitor but many people use it as such, assuming it’s superior to WD-40 (both products are from the same parent company).

Note that the Muc-Off Motorcycle Protectant featured in the review was the product offered during the first part of this test, carried out in 2018. The company's new HC B1 wasn't included as it was released just as I completed this second stage of testing. It'll be in a future test.

Before we decide which is best though, let’s look at the other criteria…

Products were coated with fine sand then rinsed to assess their stickiness – you can see here that the original Rust Blocker goes on thicker, and after rinsing holds onto a bit more sand than the new Clear Coat version.

Do these rust proofers leave a sticky residue?

There is a marked difference in the way some of these products sit on the surfaces of your bike, which is worth noting when considering what makes for the best corrosion protectant.

Flat steel plates were cleaned with 99.9% pure isopropyl alcohol, dried and coated with the protectants before being left for 24 hours. Each plate was then coated in fine sand, shaken to dislodge any excess, then rinsed with a hose.

Sand retention is rated from 0 to 5, with 5 being the most sand left on the plate…

Lower numbers are best. Products with the same score are listed alphabetically

XCP Clear Coat was released as a response to some people finding the original Rust Blocker (which is still available) to be a bit sticky; after a ride it can hang onto some fine road grit, though this will depend very much on how heavily it’s applied, and it’s worth pointing out that it doesn’t need to go on too thick.

The new XCP Clear Coat shrugged off the fine sand with ease, especially when rinsed, but keep in mind that all of these results are ball-park figures only as I don’t have the kit to weigh samples before and after with enough accuracy.

The protectants were tested for material compatibility, to ensure they can’t harm any on your motorbike

How safe are rust proofers on plastics?

In the Best Motorcycle Cleaners test I used samples of painted steel, anodised aluminium, ABS plastic, polycarbonate, acrylic and chain O-rings to ensure material compatibility.

I carried out the same test here, leaving the samples in the products for two weeks as, while they’re intended to provide a protective barrier against corrosion on metals, it’s almost impossible to apply them without getting them on the rest of the bike. Even if it’s wiped away, any product will be coating the insides of the bodywork and many other parts of the machine.

I drilled 2.5mm holes (with a pillar drill for consistency) in all the samples of the three different plastics, then carefully inserted stainless steel M3 self-tapping screws to create stress risers that highlight any incompatibilities between the material and the chemical.

In my testing, none of the corrosion protectants I sampled caused any noticeable harm to any of the materials used on motorcycles.

So, unlike some of the cleaning products I tried, you can spray the corrosion protectants (and multipurpose sprays) featured here without any worries.

Hopefully it goes without saying that ALL of these products MUST be kept away from your brake calipers, pads, discs and tyres. Do not apply them to the brake disc carriers either as centripetal force will throw them out onto the disc surface. If you’re applying any of these products with a compressor, be sure to cover your entire wheels first.

• Thanks to Evotech Performance, manufacturers of motorcycle parts & accessories, who used their UK factory to cut the samples of steel.

• Thanks to accident repair specialist 4th Dimension for painting the steel samples.

• Thanks to Skidmarx for supplying the samples of acrylic, which are offcuts from the production of their excellent aftermarket screens.

• Thanks to trail and adventure parts manufacturer Rally Raid products for supplying the aerosol lids used as sample dishes from their sister company Masplas Mouldings.

• Thanks to aftermarket and performance parts specialist B&C Express for supplying the chain O-rings.

A good corrosion protectant will keep your bike rust free for a lot longer than a poor one…

Best value corrosion protectants

When considering the price of these protectants, you need to take into account how thickly you apply them, how often, and whether they’re a multi-purpose spray, in which case they might offer you increased value.

However, it’s been out of the scope of my testing to look at lubrication performance – where relevant – and this is a test that’s purely trying to find the best way to stop your motorbike from going rusty…

We can see there’s a huge disparity between the cost of these products, but do also consider how often you’re likely to be applying them. The longer they can provide corrosion protection, the less you’ll have to use them. Also, do remember that while you may be re-applying them after washing your bike, unless you’re carrying out an extremely thorough clean every time there will be nooks and crannies that don’t always get reached, so personally I think it’s worth opting for a product that gives good long-term protection.

Recommended rust inhibitors

Based on their ability to prevent corrosion with just one application, the following products are my choices for recommended rust proofers.

A lower stickiness score is better. Products are ordered by RRP/litre

Bulldog BDX 01 was one of the big surprises, given that it’s a multi-purpose spray; to have out-performed ACF-50 (when applied in a light coat with a compressor) is very impressive. Keep in mind though that I’m only testing it as a corrosion protectant, and haven’t assessed its lubricity performance. If used solely for rust inhibiting, there are cheaper and more effective products.

ACF-50 gave poor performance compared to the other products here but it does have the advantage of being less sticky than many of its competitors. This is thanks to the fact that it stays more liquid, which is potentially why it doesn’t appear to offer the same level of protection. Applying it with a compressor will get it deep into the bike, where it will still offer good protection, but it proved less effective than cheaper alternatives.

Scottoiler’s FS365 missed out on a recommended as I’m looking for products that offer protection in just one coat. However, if you ride every day throughout winter, it’s important to keep the salt and grime rinsed off as much as possible. Using a hose is one way, and it’s clear that the best performing products in this test show little degradation from a strong rinse down, but if you don’t have easy access to a tap when you get home with the bike, FS365 could be an option worth considering, though I’d still suggest the brakes are rinsed with water as much as possible (especially if you have old Tokico six-pots).

Best Buy rust inhibitors

The best buy products have to offer good rust protection, be easy to apply and be good value…

Products are ordered by overall stickiness score, which combines ratings for before and after rinsing

TechCote ACS TC200 offers excellent performance at a relatively good price – the only thing it’s lacking over its Best Buy rivals is the ability to buy it in liquid form to apply with a compressor as its chemistry means it flashes off as it’s applied.

XCP Clear Coat is easy to apply from the spray bottle and hangs onto no more grit after rinsing than TechCote. It can also be poured straight into a paint gun’s pot and applied with a compressor. Clear Coat in an aerosol can is extremely easy to use and only missed out on a Best Buy as the bottle is better value. If you don’t mind paying a bit extra, and won’t want to apply it with a compressor, it’s worth the money.

XCP Rust Blocker is a superb product when applied with a compressor (and offers excellent value for money). If you have access to the equipment I’d highly recommend it, as the way it mists means the product reaches right up under the tank and other inaccessible areas. While TechCote provided better protection in my test than Rust Blocker when applied this way, the fact that it can more effectively reach into the smallest nooks and crannies mustn’t be overlooked.

XCP Rust Blocker from a can is the stickiest of the four Best Buys, and the most expensive, but there can be no doubt that it offers by far the best rust protection of anything I’ve tested.

How do I use ACF-50, XCP or any of the other products here?

Before applying any rust inhibitor, it’s important to get your bike thoroughly clean. Also, while many claim good water dispersing properties, you’ll get far better results if you dry the bike thoroughly.

To find out how to clean and dry your bike in three easy steps, as well as the cleaning products you really must avoid, click here.

Then it’s simply a case of spraying the corrosion inhibitor onto all the metal surfaces, avoiding the brakes and tyres. Do not apply any of them to the brake disc carriers as centripetal force will carry them onto the braking surfaces.

Avoid any overspray on matte-painted surfaces as it creates a patchy look. You can clean this off of course, but check out the cleaners review for more matte-paint care advice.

For the best results I use a Clarke Panther air compressor (always wait for the VAT-free days at Machine Mart – sign up for their mailing list or ask to be added in store), and a basic paint gun (this £19.19 one) as I find it gives a much better mist than a paraffin spray gun. Both XCP Rust Blocker and ACF-50 pass through this gin without any thinning

ACF-50 can be a little reluctant to come out of the aerosol can on a cold day, so keep it indoors for a while, or put it in some warm water.

Finally, most of the corrosion protectants here benefit from a quick wipe down with a clean microfibre cloth to remove any excess from exposed surfaces, but use that same cloth on unpainted matt-plastic and they’ll typically come up with a lovely deep, black sheen. I keep the cloth I use for this in a plastic bag so it’s already well saturated.

Personally, for most of my bike cleaning I use XCP Clear Coat in an aerosol, but on a once-a-year deep clean I will run it through the compressor. However, I also use XCP Rust Blocker in a can to spray into steel frame tubes of my bikes, and inside the swingarm when I have the wheel out; my Grom, for instance, has a cheap steel box-section swingarm so I jet a good amount of Rust Blocker into here whenever I work on the rear brakes or change tyres. For this, it’s worth splashing out £2.95 on the aerosol extension lance.

How often should I apply ACF-50, XCP or any of the other products here?

How often you have to put these on will depend on their performance, but also how often you clean the bike.

My testing shows that the best products resist hosing well, and I’d expect them to be pretty resilient against a neutral PH foam or shampoo. However, anyone riding in the worst weather will likely be cleaning their bikes more frequently and with more powerful degreasers or bike washes, so I’d suggest giving your machine a quick once over after every wash; you don’t need to use a lot.

Why didn’t you test my favourite rust preventer?

This isn’t an exhaustive list of corrosion protectants, but it does cover the most popular that were available at the time of testing. As soon as possible I’ll carry out another test, which will include the following:

• Muc-Off HC B-1 (released just as I completed this test)

• WD-40 Specialist Corrosion inhibitor

• Lanoguard Motorbike Complete Care kit

If there are any other products you’d like me to include in a future test, please let me know in the comments below.

Best rust inhibitor: Verdict

There are plenty of corrosion inhibitors out there that promise months or even years of protection, but my testing indicates that – at least for a regular winter rider who keeps their bike clean – this is might not be the case.

Motorcycles are hard to keep looking at their best because there are so many chassis and engine parts always exposed; crawl under any car and you’ll see that while they might look good on the top, it’s a different story on the bits you can’t see. In my opinion, that means it’s worth spending the money on something that offers good protection for as long as possible.

Seven-month corrosion timelapse

Watch the video explaining how this testing was done

Despite describing it as ‘an ideal winter protectant’, Muc-Off asked us to include this comment after the poor performance of its Motorcycle Protectant: “Muc-Off Motorcycle Protectant is not intended as a stand-alone dedicated corrosion protectant, it is formulated to protect your motorcycle by dispersing any remaining moisture after a thorough clean and removal of other corrosive substrates, the product therefore is not designed for the type of use seen in this test which intends to replicate a motorcycle being ridden through winter.

“Ultimately no protectant will ever be a replacement for the appropriate level of care and it is only this combined with the correct products that will help you enjoy your motorcycle all year round.”

The company’s new HC B-1 will be tested at the next opportunity.