Loctite Threadlocker is used for a wide variety of applications from automotive maintenance to the repair of common household products. Loctite is the solution to a long-time question of vibrational loosening by engineers. The old method used to involve mechanical locking devices such as split washers or nylon nuts. With these, come another set of issues, one of which is loosening under vibration. Other shortcomings include not sealing threads, requiring large amounts of several shapes and sizes, as well as being prone to rust. But fifty years ago, Loctite Threadlockers broke boundaries allowing a way to lock and seal threaded fasteners simply with a liquid adhesive. Separated by four colors, each type contains a different grade of substances to best fit the job at hand. But how do you know which one to choose? All the bottles are red with simply the different colored marking and small description on each. Well, we are here to explain to you what each is best used for.
Not sure why Loctite is the gold standard of threadlockers? Read about it here first!
Loctite Purple (222): Low Strength Threadlockers
From the lowest side of the spectrum is the Loctite Purple. This strength is perfect for fasteners less than 6mm. It’s suitable for all metal threading and is great for low strength metals that are prone to fracture like aluminum. This grade will allow for disassembly by hand tools, and the adjustment of screws including set screws. Loctite Purple is also good on calibration screws, meters, and gauges. Full cure time is about 24 hours.
Loctite Blue (243): Medium Strength Threadlockers
Next on the spectrum is the Loctite Blue. It’s a medium strength adhesive that is suitable for all metal threading as well. As a general purpose threadlocker, it’s ideal for machine tools and presses, pumps and compressors, mounting tools, and gear boxes. This strength is great for fasteners up to 20 mm. Loctite Blue is even proven to be able handle minor contamination to industrial oils. And while the strength may be medium, it still allows for disassembly by hand tools. Like the Loctite Purple, the full cure time is about 24 hours.
Loctite Red (262): High Strength Threadlockers
Loctite Red is a medium to high strength adhesive. This general purpose threadlocker will fluoresce under UV lighting to allow for quality control and monitoring. Like the other Loctite products listed, it is suitable for all metal fasteners. Loctite Red tolerated slight contaminations of industrial oils and is ideal for preventing any migration of the adhesive. If you are looking for permanent assembly, then this grade is perfect for your project. It’s medium to high strength is great for heavy equipment, suspension bolts, motor and pump mounts, as well as bearing cap bolts and studs. Any threading up to 27mm and larger in diameter will be secured by Loctite Red.
Loctite Green (294): Penetrating Threadlockers
Last on the spectrum is the Loctite 294 which is a high strength dark green fluorescent adhesive. Due to the capillary action and low viscosity, Loctite states that it works best between “engaged threads”. One benefit to this grade that is different from the others is that there is no need for disassembly before applying the adhesive. It is also great with oil coated fasteners. Loctite Green allows for removal with heat and hand tools. It’s great for preassemble fasteners, instrumentations screws, electrical connectors, and carburetors. Any threading up to 14mm can be used with this grade of Loctite threadlockers.
Loctite Threadlockers – General Information
The previously discussed Loctite threadlockers are all liquid adhesives and listed with specific numbers. Other numbers and types of adhesives are offered. With these, the description by color still applies. While the liquid may be more commonly used, sticks similar to glue sticks are also an option. No matter which kind of Loctite threadlocker is chosen, all offer good quality performance in locking and sealing of threaded fasteners with a cure rate of 24 hours. In addition to this, there is a wide range in temperature resistance from -65 degrees Farenheit to 650 degrees Farenheit, depending on the grade of adhesive.
No matter the project, it’s always important to have the best tools for the job. The old school way for sealing was mechanical and didn’t guarantee results under vibration. Loctite threadlockers secure what’s needed and don’t loosen under vibration. Once sealed, it’s done. Depending on what grade of adhesive chosen, disassembly may be permitted by heat and hand tools. But you always know with a Loctite threadlocker, your metal on metal application is secured.