Threadlock works by utilizing a unique chemical reaction that creates a strong bond between opposing threads and fills surface imperfections, effectively locking the threads in place to prevent loosening from vibration and shock. Most threadlockers are a type of adhesive known as anaerobic epoxies, meaning they cure or harden in the absence of oxygen.
When applied, threadlocker remains liquid while exposed to air. However, once a fastener is assembled, the threadlocker is sealed within the joint, depriving it of oxygen. Simultaneously, the metallic ions present on the surface of the metal threads act as catalysts. This combination of oxygen deprivation and metal ion catalysis triggers a polymerization reaction, causing the liquid adhesive to solidify into a tough, thermoset plastic.
The Anaerobic Curing Process
The core of threadlocker's effectiveness lies in its anaerobic nature:
- Application: The liquid threadlocker is applied to the threads of a fastener. While exposed to air, inhibitors in the formula prevent it from curing prematurely.
- Assembly: As the nut and bolt are tightened, the threadlocker is squeezed into the microscopic gaps and surface imperfections between the mating threads. This action also seals off the adhesive from oxygen.
- Catalysis: The metal ions on the surface of the threads, particularly iron and copper, act as catalysts for the curing process.
- Polymerization: Deprived of oxygen and catalyzed by the metal ions, the monomer liquid rapidly converts into a solid polymer, creating a strong, continuous bond that resists vibrational loosening and seals against leaks.
This process ensures that the threadlocker only cures where it's needed—within the fastened joint—and not in the bottle or on exposed surfaces.
Benefits of Using Threadlockers
Beyond simply preventing loosening, threadlockers offer several significant advantages in mechanical assemblies:
- Vibration and Shock Resistance: They fill all the voids in the thread path, preventing micro-movements that can lead to fastener loosening under dynamic loads.
- Corrosion Prevention: By sealing the threads, they prevent moisture and corrosive elements from attacking the metal surfaces.
- Leak Prevention: They create a seal that can prevent fluid or gas leakage through the threaded joint.
- Controlled Fastener Strength: Different strengths allow engineers to select the appropriate level of locking for specific applications, ensuring ease of disassembly when required.
Types of Threadlockers
Threadlockers are available in various strengths, each designed for specific applications and disassembly requirements. The color of the threadlocker often indicates its strength.
| Strength Level | Common Color | Typical Application | Disassembly Method |
|---|---|---|---|
| Low Strength | Purple | Small fasteners (e.g., screws < 1/4"), adjustment screws | Hand tools |
| Medium Strength | Blue | General-purpose, machine tools, pumps, gearboxes | Hand tools (may require more effort) |
| High Strength | Red | Permanent assemblies, large fasteners (> 3/4"), heavy equipment | Localized heat (e.g., propane torch) + hand tools |
| Wicking Grade | Green | Pre-assembled fasteners, penetrating existing assemblies | Depends on the base strength (often high) + heat/hand tools |
Application Tips for Optimal Performance
To ensure threadlockers perform effectively, consider these best practices:
- Cleanliness: Always clean and degrease threads thoroughly before application to ensure proper adhesion.
- Coverage: Apply a few drops to the leading edge of the male thread, ensuring complete coverage as the parts are assembled. For through-holes, apply to both the nut and bolt.
- Cure Time: Allow sufficient time for the threadlocker to fully cure before subjecting the assembly to load. Refer to the product's technical data sheet for specific cure times.
- Temperature: Ensure application occurs within the recommended temperature range for the specific product.
By understanding the anaerobic curing mechanism and selecting the appropriate strength, threadlockers provide a reliable solution for securing threaded assemblies against failure.
