Threadlocker vs Thread Sealant: What’s the Difference?

When working with fasteners and pipe fittings, choosing the right adhesive is essential for reliability and safety. Two commonly used products are threadlockers and thread sealants. While they may look similar, they serve very different purposes.

Understanding the difference between threadlocker and thread sealant helps ensure bolts stay secure and pipes remain leak-free. In this guide, we’ll explain how each product works, when to use them, and how to choose the right one for your application.

What Is a Threadlocker?

Threadlockers are adhesives designed to prevent bolts and threaded fasteners from loosening due to vibration. They are commonly used in machinery, automotive components, and industrial equipment where movement and vibration can cause fasteners to back out over time.

Threadlockers cure in the absence of air when trapped between metal threads. Once cured, they form a durable bond that locks the threads together.

Common Applications

Threadlockers are typically used for:

• Bolts in engines and machinery
• Gearbox fasteners
• Structural bolts
• Equipment exposed to vibration

Threadlocker Strength Levels

Threadlockers are available in different strengths:

• Low strength (purple) for small fasteners that may require frequent removal
• Medium strength (blue) removable with hand tools
• High strength (red) designed for permanent assemblies
• Wicking (green) penetrate pre-assembled fasteners

These different strengths allow users to choose the right level of locking for their specific application.

What Is a Thread Sealant?

Thread sealants are designed to seal threaded pipe connections and prevent leaks in fluid or gas systems. Unlike threadlockers, their primary function is sealing rather than locking.

Thread sealants fill the small gaps between threaded fittings, preventing liquids or gases from escaping while also protecting against corrosion.

Common Applications

Thread sealants are commonly used in:

• Plumbing systems
• Hydraulic fittings
• Pneumatic systems
• Fuel lines
• Industrial pipe assemblies

They are particularly useful where leak prevention is critical, such as in water, oil, or gas pipelines.

Key Differences Between Threadlocker and Thread Sealant

Although both products are applied to threaded components, their functions are different.

Feature	Threadlocker	Thread Sealant
Primary Purpose	Prevent bolts from loosening	Prevent fluid or gas leaks
Typical Use	Bolts and fasteners	Pipe threads and fittings
Application	Machinery, automotive, industrial equipment	Plumbing, hydraulic, and pneumatic systems
Strength Levels	Low, medium, and high	Typically designed for sealing rather than locking

In simple terms, threadlockers secure fasteners, while thread sealants prevent leaks in threaded connections.

When Should You Use Threadlocker?

Use a threadlocker when you need to:

• Prevent fasteners from loosening due to vibration
• Improve the reliability of mechanical assemblies
• Secure bolts in machinery or vehicles
• Protect threads from corrosion

Threadlockers are widely used in automotive repairs, industrial equipment, and manufacturing applications.

When Should You Use Thread Sealant?

Thread sealants are the better choice when you need to:

• Prevent leaks in pipe connections
• Seal hydraulic or pneumatic systems
• Protect threaded fittings from corrosion
• Ensure pressure-tight seals

They are commonly used in plumbing, oil and gas systems, and industrial fluid handling equipment.

Choosing the Right Product

Selecting between threadlocker and thread sealant depends on the type of connection you are working with.

If you are fastening bolts or screws that must resist vibration, a threadlocker is the correct solution.

If you are connecting pipes that carry liquids or gases, a thread sealant is required to prevent leaks and maintain system integrity.

Using the correct product ensures better performance, improved safety, and longer-lasting assemblies.

FAQs

Can threadlocker be used as a thread sealant?

No. Threadlockers are designed to secure fasteners and may not provide a reliable seal for fluids or gases in pipe connections.

Can thread sealant prevent bolts from loosening?

Thread sealants may provide some lubrication during assembly, but they are not designed to lock fasteners in place. For vibration resistance, a threadlocker should be used.

Do threadlockers seal threads?

Some threadlockers can provide minor sealing properties, but their primary function is preventing loosening rather than sealing pipe connections.

What is the best product for pipe threads?

Thread sealants are specifically designed for pipe fittings because they fill gaps in threads and prevent leaks in fluid or gas systems.

Do thread sealants require curing time?

Many anaerobic thread sealants cure after assembly and may require several hours to reach full strength depending on temperature and materials.