What in the world is the difference between blue and red Loctite?! It’s frustrating, isn’t it? I love Loctite products, but navigating through their catalog of threadlockers is pure hell. It’s like a labyrinth. That’s why I decided to write this short guide and help you out. Let’s figure out what their color scheme stands for.
I’ll be focusing on these three different types of Loctite:
- Blue (Medium-Strength): Loctite 243 vs 242
- Red (High-Strength): Loctite 262 vs 271 vs 272
- Purple (Low-Strength): Loctite 221 vs 222
So, take your pick from the Table of Contents:
Medium-Strength Series: Loctite 242 vs 243
Both the 242 and 243 are from Loctite’s medium-strength Blue threadlocker product line. You’ll use them to prevent any fasteners from getting loose from vibrations or experienced shocks. Both share the following common properties:
- You should use them with 1/4″ to 3/4″ bolts.
- Their temperature range maxes out at 360°F.
- You can remove them with standard hand tools.
The fixture time for both is only 10 minutes, while full cure comes after 24 hours. These work great with steel or stainless steel, as well as most plated fasteners. Both have decent anti-corrosion tolerance and mild resistance to most protection fluids too.
But, of course, they’re not exactly the same…
The Big Difference Between Loctite 242 and 243
One major difference is that Loctite 243 comes with significantly improved oil tolerance. Even if your threads are a little dirty and oily, it’s not a big deal. No need to use any primers on plated fasteners either. But if you work with a tube of Loctite 242, you will have to clean all threads properly if you want the Threadlocker to work at all.
Sure, this might seem like a very small difference, but things get sticky and oily all the time! That’s why I do appreciate the time-saving side of the Red 243 Loctite.
- Better oil tolerance for easier application
- Great longevity.
Now, some people say that the 243 is also a little bit stronger. Honestly, I haven’t noticed a big difference in that department. I personally consider them the same in terms of strength.
My recommendation: Loctite 243 (check prices).
High-Strength Threadlocker Series: Loctite 271 vs 272 (and 262)
As a preface: these are Loctite’s high-strength Red threadlockers. If you want to remove them, you’ll have to use heat and sweat a bit over your hand tools. They’re pretty hardcore.
When you compare these three, the 272 is the most heavy-duty adhesive. Both in terms of heat resistance and the supported size of your fastenings. So, this is the safest choice if you want to be sure that the adhesive will withstand the working temperature and the fastener size. But in case you know what strength is recommended for your application, 272 or 262 might be just fine as well.
Again, all of these threadlockers cure fully at the 24-hour mark.
This series is perfect for more heavy-duty automotive use, like keeping those shock mounts tight.
Important note: Do not confuse Loctite 262 with Loctite 2620! Loctite 2620 is harder to find and is the brand’s most heat-resistant beast yet. It goes up to 650°F!
Low-Strength Series: 221 vs 222 Loctite Threadlockers
Finally, we’re coming to the low-strength Purple threadlocker series from Loctite. These are perfect for general use and extremely easy to remove after application. Is there a difference between Loctite 221 and its counterpart – the 222 Threadlocker? Very little.
In my experience, these low-strength threadlockers are actually interchangeable. We’re talking about low-strength, low-viscosity adhesives for small threads. General household needs or very low torque stuff like scope mounting are perfect usages here.
The only slight difference is the breakaway torque. On 221, the torque is 8.5 Newton meters, while it’s 6 Newton meters for the Loctite 222.
- Easy, cheap solution for general household needs.
- Easier to breakaway than 221 so it’s more convenient too.
Otherwise, both threadlockers share the following properties:
- They work with small screws under 1/4″
- They withstand up to 300°F
- Fixture time is quite fast – 10 minutes, sometimes even less. Like other Loctite threadlockers, the full cure time is 24 hours.
Which Adhesive Threadlocker Will You Choose?
Whew! I think I covered the most common Loctite threadlocker types: Blue vs Red vs Purple. I hope this was both easy to understand and explanatory enough for you! With all these comparisons and explanations, you should be able to choose the ideal option from Loctite’s wide range of threadlockers.
Fun fact: Permatex also uses the same color scheme! If you want to learn more about them, check out my post on Loctite vs Permatex, where I compared the two brands.
As I mentioned, if you want me to cover any other Loctite series or add some complementary information – let me know!