Threadlocker is a specialized adhesive used to secure metal fasteners, such as bolts and screws, and prevent them from loosening due to vibration, shock, or corrosion. Commonly used in automotive, industrial, and machinery applications, threadlocker helps maintain assembly integrity by locking threaded fasteners in place.

Threadlocker is an anaerobic adhesive, meaning it cures in the absence of oxygen—specifically, within the threads of tightly assembled metal parts.

How Does Threadlocker Work?

1. Application

Apply the liquid threadlocker to the threads of the fastener before assembly.

2. Assembly

As the bolt or screw is tightened, air is displaced from the threads, creating the oxygen-free conditions needed for curing.

3. Curing

The adhesive cures into a rigid thermoset plastic, locking the fastener and sealing micro gaps within the threads.

4. Sealing and Protection

Once cured, threadlocker provides a protective seal that helps prevent rust, corrosion, and leakage.

Threadlocker Strengths and Colors

Most manufacturers (like Loctite) use a color-coded system to indicate the strength and removability of their threadlockers:

🔵 Blue Threadlocker (Medium Strength)

• Best for: General-purpose fasteners up to 20mm that may require periodic maintenance

• Common uses: Engine bolts, machine screws, pump housings

• Removability: Can be removed with standard hand tools

🔴 Red Threadlocker (High Strength)

• Best for: Permanent installations and heavy-duty fasteners up to 25mm

• Common uses: Automotive suspension bolts, heavy machinery

• Removability: Requires localized heat (~450°F / 232°C) for removal

🟢 Green Threadlocker (Wicking Grade)

• Best for: Pre-assembled fasteners or hard-to-reach areas

• Common uses: Electrical connectors, set screws

• Removability: Medium-to-high strength; may need heat on large fasteners

🟣 Purple Threadlocker (Low Strength)

• Best for: Small screws under 6mm or fasteners that require frequent removal

• Common uses: Eyeglasses, electronics, laptop screws

• Removability: Easily removed with hand tools

How to Apply Threadlocker Correctly

1. Clean the Threads

Use a parts cleaner or solvent to remove grease, oil, dirt, or old adhesive from both internal and external threads. Allow them to dry completely.

2. Apply the Threadlocker

• Through holes: Apply a few drops to the bolt where the nut will sit.

• Blind holes: Apply drops to the bottom of the internal threads.

3. Assemble and Tighten

Quickly assemble and torque the fasteners to specification. The adhesive will spread throughout the threads.

4. Cure Time

Allow 24 hours at room temperature for a full-strength bond. Use a threadlocker activator to speed up cure time if needed.

When to Use Threadlocker

• Preventing vibration loosening in automotive and aerospace applications

• Sealing threaded connections in hydraulic and pneumatic systems

• Corrosion protection in outdoor or marine environments

• Reducing maintenance by eliminating the need to retighten bolts

Choosing the right type of threadlocker ensures fasteners stay secure under tough conditions. Whether you’re working on automotive repairs, industrial machines, or small electronics, using threadlocker properly prevents loosening, improves safety, and extends the life of your equipment.