What’s the difference between Loctite 242 and 243?
Loctite 243 cures slightly faster and is less sensitive to surface cleanliness than Loctite 242, making it a better choice for medium-strength applications. Unlike Loctite 242, which requires a clean, dry, non-greasy surface on both items being connected and only works with ferrous materials, Loctite 243 works with any material and is more versatile while offering similar functional characteristics to 242.
Loctite 242 vs. 243: Specs & Uses
🔥Max Service Temperature
Loctite 242: 300°F (149°C)
Loctite 243: 180°C
🆚Key Substrates
Loctite 242: Ferrous metals
Loctite 243: Ferrous and non-ferrous metals, plated surfaces
🛠️Common Uses
Loctite 242 can be used to secure lens retaining rings, eyepieces, and optics kits; prevent bolts and nuts from vibrating loose in various parts of your vehicle, such as pellet gun bolts, and rolling floor jack bolts; improve GPU screw stability
Loctite 243 is suitable for use on threaded fasteners made of any material, including zinc-plated nuts and non-plated bolts; offers a wide service temperature range of -55 to +180°C, making it suitable for applications in extreme temperature conditions.
Technical Info
My Hands-on Test of Loctite 243 (Threadlocker)
The 243 threadlocker has more manageable holding power than red threadlockers (which can have break strengths of 150-200 in-lbs for 3/8″ plain nuts).
✅The Holding Power of Loctite 243
With regard to holding power, 243 works well on zinc-plated nuts, non-plated bolts, and passive substrates like stainless steel. It’s important to note, however, that this product isn’t designed for waterproofing or sealing applications. There are specific Loctite products for those jobs.
What sets 243 apart is its combination of versatility and performance. It’s designed to be a step up from general purpose thread lockers like the 242 formula. While 242 is readily available, 243 is specially formulated to withstand more extreme conditions involving oils, higher heat, and high torque bolts/nuts. This makes it ideal for use on engine components, drivetrain fasteners, and anywhere vibration can cause stubborn nuts/bolts to work loose over time.
The temperature rating is one of 243’s strengths – it can handle a very wide operating range from -55°C to +180°C (-67°F to 356°F). This thermal resistance ensures it won’t degrade or allow fasteners to loosen, even in blazing hot engine bays and exhaust areas. The medium strength lock is also perfect, preventing accidental unlocking but still allowing disassembly with hand tools if needed.
Loctite 638 vs. 640: Repairing Crankshaft Oil Seals Under High Heat Environments
What really sold me on 243 was its ability to reliably cure and lock threads on virtually any substrate material. It works beautifully on easier to lock active metals like brass and copper. But it also provides a tenacious lock on harder-to-lock passive substrates like stainless steel and plated surfaces that can sometimes cause adhesion issues. I’ve used it on everything from zinc plated nuts to non-plated bolts with zero issues.
Loctite 222 vs. 243: One Component, No Mixing for Eyeglass Repair, Philips Head Screws in Shower Controls
While not a waterproofing material per se, 243 does offer some water and moisture resistance once fully cured between mated threads. This liquid product won’t cure properly if the threads are wet during application though. Its resistance to oils, solvents and chemicals is also a big plus.
It cures in about 20 minutes, but Loctite recommends waiting 24 hours before applying heavy loads or equipment that will experience high vibration or shock. Those oversized bottles with lots of air space may look underfilled, but that air gap is actually necessary to prevent premature curing of the anaerobic formula inside the container.
In my experience, 243 can be used successfully on non-metal components like canvas, fabrics and certain plastics too. I’ve locked awning fittings, boat canopy screws and more using this versatile thread locker. While not a primary use case, it works in those situati
If you own an older Harley Davidson motorcycle, Loctite 243 is an absolute must. Otherwise, you’ll find yourself constantly replacing lost fasteners that have vibrated loose. Loctite 243 is specifically designed for securing threaded fasteners and preventing them from loosening due to vibrations. It forms a strong bond that keeps bolts, nuts, and screws in place, providing added safety and preventing potential damage.
❌One Downside
Once you loosen and remove a fastener locked with 243, the broken seal means you’ll need to reapply fresh 243. The cured compound can’t be re-activated. But that’s a minor inconvenience for the reliability it provides. Just be sure to check the expiration date, as 243 does have a shelf life (typically 12-18 months).
💬 FAQ of Loctite 243 (Threadlocker)
Q: What are the benefits of using Loctite 243 Vs. Loctite 242 for medium-strength applications?
A: Loctite 243 cures slightly faster and is less sensitive to surface cleanliness than Loctite 242, making it a better choice for medium-strength applications. Unlike Loctite 242, which requires a clean, dry, non-greasy surface on both items being connected and only works with ferrous materials, Loctite 243 works with any material and is more versatile while offering similar functional characteristics to 242.
Q: Can Loctite 243 be used to stop diesel leaks from threaded joints?
A: Loctite 243 can be effective in stopping diesel leaks if the threads are cleaned properly before application.
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What Is Loctite 242
✅How to Apply Loctite 242
Surface preparation is crucial for curing. Before applying Loctite 242, the threads must be thoroughly cleaned with a solvent like rubbing alcohol to remove any oils or contaminants. Failure to do so can result in the adhesive not fully curing, as I learned when testing it on some dirty threads. Even after 24 hours, a simple paper towel could wipe away the uncured Loctite.
Application is a breeze once the surfaces are prepped. Simply apply a small amount of the blue liquid to the clean, dry threads before assembly, and then tighten the components together. The anaerobic formula ensures that the adhesive only cures when confined between the mating surfaces, eliminating any mess or accidental bonding.
One important tip – for screws with very fine threads or small gaps like those on eyeglasses, opt for the lower viscosity Loctite 222 instead of 242. The 242 is better suited for larger threaded fasteners.
Loctite 222 vs. 243: One Component, No Mixing for Eyeglass Repair, Philips Head Screws in Shower Controls
For larger gaps like pipe fittings, while the thicker 242 can work, I’ve had better luck using traditional pipe dope or thread sealant tape. The Loctite is better for smaller gaps and preventing loosening rather than sealing huge joints.
Speaking of large projects, I once used the 242 to join two 20-foot pipes together for an outdoor weather station mast. It held up beautifully to rain, heat, and harsh conditions over several years.
But what really sets Loctite 242 apart is its removability. Unlike permanent red high-strength thread lockers( Loctite 270), this medium strength formula allows for disassembly with hand tools if needed. This removability is particularly handy for projects like bed frames, where you may want to take things apart in the future.
Loctite 263 vs. 270: Sealing Bolts, High strength, Passive Substrates(Stainless Steel, Aluminum & Plated Surfaces)
Shower Door Roller Screws
I also had success using Loctite on shower door roller screws that had become undone. Applying the adhesive ensured that the screws stayed in place, effectively solving the problem. I am even considering using it on my fridge door handle, which tends to come loose frequently. I used a needle to open the tube, and it proved to be a wise choice.
Now, one amusing anecdote – a friend once joked about using Loctite 242 as a denture adhesive. While I can’t recommend testing that one out, it did give us quite a laugh imagining the potential taste sensations!
❌One important note
While Loctite 242 is fantastic for most threaded metal fasteners like steel and stainless steel, it’s not recommended for assemblies involving plastics or composites. The solvents in the formula can potentially cause crazing or cracking on those materials over time.
FAQ of Loctite Threadlocker Blue 242
Q: Does Loctite Blue 242 harden? I applied it to a thread for testing, but after 24 hours, it was still in liquid form and could be easily removed with a paper towel.
A: Yes, Loctite Blue 242 does harden. Before using it, make sure to shake the bottle well. Apply a drop of the product to the fastener threads, ensuring you use a minimal amount. Tighten the fastener to prevent loosening, and wipe off any excess while it’s still wet. Remember to cap the tube tightly. If you need to reopen the tube in the future, you can use pliers and a pin or small nail. Loctite Blue 242 has proven effective for keeping fasteners secure while allowing for future removal if needed.
Q: Can I apply this to an already tightened bolt without removing it?
A: Loctite Blue 242 is intended for use during installation and not for already assembled or installed bolts. I would recommend removing the bolts and re-installing them with Loctite Blue 242 for optimal effectiveness.
Q: Will this work on stainless steel bolts?
A: Loctite Threadlocker Blue 242 is particularly suitable for applications involving less active substrates like stainless steel and plated surfaces, where disassembly may be required for servicing. Have a great day!
Q: What is the shelf life of the Blue 242? If I open it, use it once, and then store it, how long will it remain effective?
A: According to Loctite, the shelf life of Blue 242 is two years. However, many users have reported it lasting longer. I have personally used a tube that I opened four years ago, and it still appears to work well.
Q: Will Loctite Blue 242 work for securing a bolt in a power rear gate? I had to replace the entire motor because the bolt came out and stripped the threads.
A: No, Loctite Blue 242 will not work in that situation. I recommend using Red Loctite instead( See loctite 515). Ensure that the bolt is clean and free of any oil residue before applying the Red Loctite. Allow it to dry for at least an hour, or longer if possible.
Q: Is it safe to use this as a denture adhesive?
A: Yes, Loctite Blue 242 can be used as a denture adhesive. I have personally used it for ten years now, although I must say that it does affect the taste of corn.
I’m Ronald Stevens, a Mechanical Engineer obsessed with adhesives, glue, and all things sticky! My passion began in childhood when I’d always be the one playing with glue during arts and crafts. And I’d spend hours researching and experimenting. Happy reading, and remember: stick with the best, and you’ll never be stuck in a mess!
Feel free to contact me and join our discussion:
Should I apply Loctite Blue 242 to the doorknob set screw before or after screwing it in? Do I put a drop on top?
It's best to apply this to the screw threads before screwing it in. Make sure to use a very small amount, and apply it before the screw is fully inserted. Remember, less is more in this case.