An Introduction to Threadlocker Adhesives

What Are Thread-Locking Adhesives?

Thread-locking adhesives, also known as threadlockers or thread sealants, are specialized adhesives that have been around since the 1950s. Specifically designed to keep vibration, thermal expansion, or other external forces from loosening mechanical fasteners, they play a vital role in safety, manufacturing, and maintenance across a range of industries.

This blog will delve into the world of threadlocker adhesives, including the different types of threadlockers, their formulas and strengths, and how they work. Read on to learn more. 

Why Use Threadlocker Sealants?

While some industrial-strength tapes are on par with threaded fasteners, there are numerous applications where it makes more sense to use hardware. But as integral as they are to assemblies, fasteners are not foolproof. Despite their reliable and predictable nature, they can also reliably and predictably fail over time when subjected to repeat stressors like vibration, heat, and more. For this reason, experienced assemblers depend on threadlocker sealants. 

Thread-locking sealants do more than keep threaded fasteners secured, however. They can also reduce the effects of corrosion and prevent leaks in assembled parts, making them a key component of safety in the following industries: 

  • Automotive repairs and maintenance: Threadlocker adhesives are used in the automotive industry to secure bolts and nuts in vehicle parts like an engine or transmission.
  • Manufacturing and assembly: Threadlocker is used in the manufacturing and assembly of machinery, equipment, and other products to secure fasteners on power tools, electronics, and appliances.
  • Construction and building maintenance: Threadlocker is used in the construction industry to secure bolts and screws on outdoor lighting, handrails, and signage.
  • Aerospace and defense: Threadlocker is used to prevent the loosening of critical components on an aircraft that could lead to catastrophic failure.
  • Marine applications: Threadlocker is used in marine applications to secure bolts on boats, dock equipment, and other marine hardware.

Whether it's keeping an engine from rattling around as a car speeds down the freeway or ensuring the wings of an aircraft do not break during take-offs and landings, for industries where fastening strength and durability cannot be compromised — threadlocker adhesives are a must. 

How Do Threadlockers Work?

Because they require the absence of oxygen to cure, threadlockers are classified as anaerobic adhesives. When applied to fasteners like nuts, bolts, and screws, they fill the space between the threads to provide resistance to loosening and secure them in place. As the fastener gets tightened, the pressure pushes any remaining air out while spreading the adhesive evenly between the threads to ensure the threadlocker can be activated to form a strong bond. 

Keep in mind that threadlockers also need active metals like iron, plain steel, copper, or brass, to initiate the curing process. In the presence of metal ions, they crosslink and polymerize to form a strong and durable bond. Fasteners or substrates composed of inactive metals must be primed with an activator first.

How Long Does It Take Thread-Locking Fluid To Cure?

The curing time for thread-locking fluid can depend on a few different factors, such as: 

  • The type and strength of the adhesive used
  • The temperature and humidity of the environment
  • The material that the fastener or substrate is made of

Typically most threadlockers will cure within 24 hours, although some may cure more quickly at elevated temperatures. Regardless, it's important for the adhesive to fully cure before using the fastened assembly to ensure maximum performance and strength.

Types of Threadlockers

Because the wrong type of threadlocker can result in mechanical failure or damage, it's crucial to understand how the different formulas, their strengths, and even the colors they come in can affect your application. Simply put, there are three main types of threadlocker adhesives:   

  1. Low-strength threadlockers: These are designed for fasteners that require frequent maintenance, adjustment, or disassembly. Low-strength threadlockers are also known as "removable" threadlockers, as they allow for the easy removal of fasteners with standard hand tools.
  2. Medium-strength threadlockers: These are used for fasteners that require a stronger hold but still need to be disassembled for maintenance or repair. Medium-strength threadlockers are also known as "semi-permanent" threadlockers, as they require hand tools and sometimes localized heat to remove the fastener.
  3. High-strength threadlockers: These are designed for permanent fastening applications, where the fastener should never come loose. High-strength threadlockers are also known as "permanent" threadlockers, as they require specialized tools and localized heat to remove the fastener.

In addition to the above types, specialty threadlockers exist for specific applications or environmental conditions. For example, some threadlockers are formulated for high-temperature or high-pressure environments, while others are designed for wet or corrosive environments.

Does The Threadlocker's Viscosity Matter? 

Threadlockers also come in a variety of viscosities that allow them to be applied pre- or post-assembly. The benefits of higher-viscosity threadlockers are that they can fill larger gaps, are more resistant to chemicals or solvents that may come into contact with the fastener, and can endure greater shear force. 

On the other hand, lower-viscosity threadlockers offer better penetration, making them ideal for maintenance and post-assembly touch ups without needing to disassemble the parts. They can also cure faster, leave less residue, and be more compatible with some materials than others.

Need Help Selecting A Threadlocker Product?

Here at, we always recommend following the manufacturer's instructions to ensure you have the appropriate threadlocker strength and type for your specific application need. 

But with so many brands and products out there, we know that finding the right thread sealant for a project can be overwhelming. If you are still unsure which threadlocker product is right for you, please do not hesitate to consult with one of our experts.

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