There are few things more annoying than being halfway through a job and encountering a seized bolt, that you just cannot free for love nor money!
Usually, it is rust, caused by moisture attacking the unprotected metal, that has grown around the bolt and is preventing you from turning it.
You may have tried a few whacks with a hammer if you can get to the offending bolt with a hammer that is! You may have tried every wrench in your toolbox or enlisting the help of a bit of muscle!
If you still can’t shift it, its time to turn to oil for help. In fact, a good quality, lubricating penetrating oil should have been your first option.
Just 1 or 2 sprays and a little patience as it works its magic, is all it should take.
Comparison Table of 10 Best Penetrating Oil for Rusted Bolts
We have compiled a guide of the 10 best penetrating oils for rusted bolts, to help you make an informed choice on which will work best for your job.
1. Kano Aerokroil Penetrating Oil
If you’re already familiar with Kroil, the penetrating oil, this is its brother, Aerokroil, same product but in a handy aerosol can. They both hail from Kano laboratory and claim to creep into the tiniest of gaps. One-millionth of an inch tiny!
Aerokroil is supplied with a handy straw to make application into the most awkward space easy. Don’t worry if you lose the straw, the jet sprayed is harsh and direct.
There is virtually nothing that this product can’t free. Metal joints will be loosened in minutes, seized car components will release.
The metal will not be affected as dried grease and oil will simply wipe away after a quick spray, gum residue will just dissolve.
The oil can displace water, prevent rust and has superb lubrication abilities.
It is great for heavy-duty applications or those small niggly jobs around the house.
It is safe for use on frozen water valves and hoses and will even release previously seized rusty bathtub faucets. A little elbow grease and a couple of sprays of Aerokroil and they will come up like new.
2. Kano SiliKroil Penetrating Solvent
This is a very similar product to Aerokroil but has added silicone. This greatly enhances its lubricating qualities and also leaves a moisture repellent coat. It won’t just resist water, it will repel it.
This is a perfect product if you are going to use it on something that gets exposed to rain or other harsh weather conditions.
Trailer, R.V. and boat owners will usually have a can stashed away somewhere.
The smallest of spaces will be lubricated, Kano state that all of their oils can penetrate gaps of one-millionth of an inch.
If you have particles of iron oxide bonded together forming rust clusters around metal joints, a spray or 2 of SiliKroil will dissolve the rust and avoid further corrosion.
It is supplied with a tube to direct the spray exactly into the target area.
3. B'laster - 8-PB - Penetrating Catalyst
This penetrating oil contains highly concentrated formulae that quickly breaks down surface tension by seeping into the most minute gaps and difficult to reach cavities.
It was designed over 50 years ago by B’laster for the automotive, hardware and marine industries and has long been the choice of professionals.
Because this lubricant refuses to evaporate, it creates a film-like layer to prevent further rusting.
It is tolerant of temperatures up to 152°F. This makes it the perfect oil for exhaust, brake, and suspension system jobs.
Its fantastic lubricate and penetrative qualities will help save time, no need to drill or burn out seized bolts. Bolts and nuts that have been rusted on for many years can be freed with just a few squirts of this PB oil.
4. WD-40 Multi Purpose Lubricant
It would be hard to find a garage or shed that doesn’t already have a can of WD-40 knocking around somewhere.
It is a great value product that someone will have picked up for a squeaky door hinge or a rusty bike chain.
This fantastic little product offers so much more than that. It can drive out moisture to protect exposed electrical systems from short-circuiting. That moisture repellent feature also shields against rust and corrosion.
It is great for removing sticky residue from things, not only is it safe for metal, but also rubber, wood, and most plastics.
It can lubricate pretty much anything, it will adhere itself to moving parts and stay there to ensure things run smoothly.
Finally, it has unrivaled rusted bolt penetrating properties. A squirt or 2 and bolts will free up in no time.
5. Gibbs Brand Lubricant (2-12oz cans)
This penetrating oil from Gibbs can be found in many mechanic’s workshops and body shops as their favorite go-to lubricant.
It promises to not only lube your metal goods but to also keep them protected for up to 5 years.
The water repellent and corrosive inhibitors make it an ideal product for use on machinery, tools and many car components, including all brake parts. Spraying this oil onto electrical connectors will help prevent oxidation.
It works in temperatures as low as -40°.
Gibbs lubricant will stop, reverse and eliminate the signs of corrosion. So once you have released those heavily rusted on bolts, you shouldn’t have to do it again. The metal will now be protected for 5 years.
Gibbs’ is safe for use on chrome and painted surfaces too, it leaves no yellowing after-effects.
6. Royal Purple 05000 Maxfilm Multipurpose Penetrating Lubricant
If your hardware is really old and crusty, then we can’t recommend this product highly enough for the job. Not only will the oil deeply penetrate and free the bolt but it will also step up a gear and provide superb lubrication.
The high-strength Maxfilm leaves a coating that ensures your metal is rust and corrosive proof for a very long time.
It’s perfect for use on power and garden tools, gears and rollers and works extremely well as gun oil.
Parts can be preserved when soaked in a coating of Maxfilm, it can also be used as a tapping fluid.
Overall, there should be a can of Royal Purple Penetrating Oil in every good toolbox!
7. Liquid Wrench L116 Penetrating Oil
Liquid Wrench is a family run business and has been for 75 years, so they kinda know what they’re talking about when it comes to penetrating oils for rusty bolts.
This 12 oz bottle has a nozzle applicator that is ideal for larger, extremely seized on bolts, locks, and hinges. Just apply the oil generously and give it a chance to soak in. Bolts that have been stuck for days and you’ve used all force on, will free up as soon as the oil has cut through the grease and dissolved all of the rust.
If you prefer aerosol, they are available too.
It contains Cerflon, a polymer that adds superior lubricity and durability. Protecting your metal parts with Liquid Wrench will extend their service life.
It performs consistently well. It is safe on paint and plastic surfaces and has low odor.
8. Andy's Super Oil - World's Best Spray Lubricant
This is a relatively new oil to the market and makes some big claims, “The World’s Best Spray Lubricant”!
Its unique selling point is deep within its formulation. Unlike other oils that simply displace water, Andy’s Oil lubricates too. A deep, long-lasting lube. So once your bolts are freed, that’s the way they will stay for a very long time.
It consists of foaming agents that get it to the point of the problem and then it isn’t too thin to drip away, it stays put.
It doesn’t leave a waxy residue as some other penetrating oils might, so it doesn’t attract dust and dirt.
It is economical as it will work on first impact, and keep on working, without the need for constant reapplication.
9. Castle Thrust Penetrating Oil
Castle has formulated this penetrating oil using foam technology, where you spray it is where it stays, it won’t run off or drip. Perfect for indoor use as there will be little or no mess.
It also has active ions so it won’t break down, even under harsh conditions and high temperatures.
It has a powerful action that can penetrate deep into corroded and rusted joints. It is so high performing that 1 spray left to soak in for 3 minutes, will be enough to loosen your seized, rusted or frozen bolt.
It is suitable for many uses, automotive, marine, household, and lawn. It is becoming an ever-popular choice in professional workshops too.
10. B'laster 16-PB Penetrating Catalyst
B’laster has had a number 1 selling penetrating oil since 1957 so you can be assured of quality.
This 16-PB oil is designed to save you time and will allow your tools to stay in top shape. Just a squirt or 2 onto rusted and frozen bolts, caused by corrosion and oxidation and you will simply be able to free them. No bashing with hammers or struggling with wrenches will be required.
It gives superior results due to the way it attacks rust, not just straight on, it smothers it and assaults it from every angle. This enables it to work quicker, speeding up the job.
The lubricant will not evaporate, ensuring it stays in place and continues to protect your bolts and equipment from further problems.
It can tolerate high temperatures so is perfect for automotive use. Though it has multitudes of uses around the home, indoors and outdoors.
Why bolts rust
Rust refers to iron oxides that form in iron-based metals and metal alloys. Other kinds of corrosion can happen in different metals.
Water and oxygen combine causing iron oxides to harden and form a coating along the metal’s surface. This will become so stiff that it will prevent any free movement of the parts.
Certain conditions can speed up the rate at which nuts and bolt rust or corrode, such as moisture exposure or humid climates.
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What is penetrating oil
Commonly penetrating oil is much less viscous (thick) than other oils. This is because it needs to penetrate and seep into the tiniest crevices imaginable, that have formed as rust around bolts, and other metal parts.
It will creep around threads and lubricate them enough to break the bonds that hold the rust together. This should allow them to be turned again.
Some penetrative oils are mixed with other ingredients to not only help them eat-away at the rust but to form a barrier that keeps the metal well protected that rust can’t cause a problem again for some time.
Main purposes of penetrating oil
Lubricating: Freeing up oxidized valves, joints, and bolts. Low-viscosity oil deeply penetrates cracks and works to loosen frozen components.
Rust and corrosive prevention: Once sprayed and freed, mechanical parts will be protected from further attacks from moisture and rust.
Water displacement: Ever wondered where the WD in WD-40 came from? Look no further. Metal needs to have a water-resistant coating to prevent rusting. Penetrating oils provide this. The oil repels moisture and keeps components protected for longer.
Cleaner: Penetrating has the ability to remove stagnant grease and grime from surfaces. Gum, varnishes and other debris won’t build up. Dirt and dust will be repelled from the oily surface too.
Quietening: Metal-on-metal grating sounds, squeaky door hinges, and springs can all be resolved with penetrating oil.
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Can penetrating oil just be used for loosening seized nuts and bolts?
No! Although they are all brilliant for lubricating seized metal joints they can be used for hundreds of other tasks. Squeaky door hinges, trampolines, and metal bed frames will benefit. So will big jobs on vehicles, brake and suspension systems, even exhausts can be cleaned and protected. Locks that no longer work, water pipes that have fuzed and hoses that have frozen. All can be restored with penetrating oil.
I keep seeing that penetrating oil is good for unfreezing things, will it work on my chest freezer?
HaHa, when we use the term frozen, we are not referring to cold temperatures, just that rust has frozen something solid, unable to move.
Is penetrating oil flammable?
It is extremely flammable, therefore should be used only as per instructions and with great care.
What does low viscosity mean?
It refers to how thick or thin a liquid is. Penetrating oil is very low viscosity, meaning it is a very thin fluid, enabling it to get into all of the cracks and crevices of a rusted bolted.
It leaves an oily film in the surface pores which forces out(displaces), other foreign materials such as water, rust, and dust.
On some of the less well-made brands, this low viscosity is what causes the fluid to run away and drip, creating a mess. More advanced brands have introduced technology into their design which enables the oil to grip tightly to the metal on contact.
Some companies use foam in their oil to achieve this same outcome.
I have generously sprayed this bolt and waited 5 minutes, just as the instructions say, still I can’t move it. What am I doing wrong?
Not all seized bolts will behave as we would like. If you have bought the correct product for the task then all that you need is patience.
The corrosion around the bolt may have taken days, weeks or even months to develop, give the oil a little time to penetrate deeply and to work its magic.
Sometimes you may have to wait a couple of hours or leaving it overnight should do the trick.
My trailer is very often found in a marine environment as I love fishing, should I use penetrating oil more?
Absolutely. Long after the lubrication has done its job, the oily, film will have been left to prevent rust and corrosion.
This would work particularly well for you, salt and water will not be able to penetrate the barrier the oil has left. Your vehicle parts will be well protected.
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The Bottom Line
If you have read through this whole article then you will realize that penetrating oils are multi-functional. While they are fantastic to keep in the garage for the home vehicle enthusiast there are also a million and one jobs around the home that you can use it for.
Finding the best penetrating oil for rusted bolts is not a straight-forward task. Don’t forget, the most expensive isn’t always the best, the least expensive may not be the worst.
Hopefully, this guide will help you decide which is best for your requirements.