Anaerobic adhesives and the type of material

Anaerobic adhesives and material type – threadlocking

Does the bonded material matter?

Yes. Anaerobic products are designed to work with metals, but the curing rate depends on the so-called material activity. In practice, this means that on some metals the joint may “grab” faster, while on others it may cure more slowly — even when using the same product.

Passive metals have weaker catalytic properties, which is why an activator is used to speed up the process or support curing under more demanding conditions. On active metals, curing usually proceeds more efficiently without additional support.

Active vs passive metals – what does that mean in practice for threaded joints?

Active materials (e.g. iron, copper) promote faster curing of threadlocking products. Passive materials (e.g. stainless steel, aluminium, chromed surfaces) may extend curing time — in such cases, application conditions become especially important and an activator should be considered.

Practical note: anaerobic adhesives are intended primarily for metal-to-metal joints. In mixed applications (metal + plastic part), plastics do not catalyse curing the way metals do, so such cases require more careful product selection.

Most common threadlocking mistakes and how to avoid them

⚠️ No degreasing – oil and grease on the thread can significantly reduce curing performance. It is worth removing contaminants from the thread before application.

⚠️ Too large a gap or too much clearance – the larger the gap, the harder it is to achieve fast and full curing. In such cases, an activator is considered more often.

⚠️ Low application temperature – curing usually slows down in cold conditions. If time is critical, an activator may help.

⚠️ Moving the joint during curing – the joint should remain stable until initial strength is achieved.

⚠️ Choosing “by eye” without thinking about disassembly – for serviceable joints, medium strength is selected more often. High strength is usually chosen where maximum resistance to loosening is the priority.

Selection in 30 seconds – quick checklist

✅ 1) What metal is it? active or passive (e.g. stainless steel / aluminium / chrome = often slower curing)

✅ 2) What are the process conditions? temperature + gap size (low temperature / larger gap = consider an activator)

✅ 3) Does the joint need to be serviceable? if yes, medium strength is often chosen

✅ 4) What about vibration and loads? the greater they are, the stronger the case for high strength

Choosing the right product for threaded joints – example solutions

When selecting a product for threaded joints, the most common factors considered are: strength (medium / high), operating conditions (vibration, temperature), possibility of disassembly, and material type (active / passive). Below are example products for threaded applications:

Medium strength – universal threadlocking

LOCTITE 243 is a product used to secure threaded joints against loosening and at the same time to seal them. It is selected for many service and industrial applications where the joint should remain secure, but still potentially serviceable.

LOCTITE 243 50 ml – threadlocking, medium strength

High strength – when vibration and loads are greater

LOCTITE 2701 is a solution for stronger locking of threaded joints. In practice, it is often selected for assemblies where high resistance to loosening due to vibration is the priority, while its fluorescent property can support application control.

LOCTITE 2701 50 ml – threadlocking, high strength

Activator – support for passive metals and demanding conditions

On passive metals, at low temperatures, or with a larger gap, curing time may become longer. In such cases, an activator is used, for example LOCTITE SF 7649, applied to one of the surfaces before the threadlocking product.

LOCTITE SF 7649 150 ml – activator for passive metals

FAQ – anaerobic threadlocking adhesives

Why does a threadlocking product cure more slowly on stainless steel?

Stainless steel is a passive metal with weaker catalytic properties. Curing time may be longer, especially at lower temperatures or with a larger gap.

Is an activator always necessary?

No. On active metals, curing usually proceeds more efficiently. An activator is most often helpful on passive metals and under more demanding process conditions.

What has the greatest effect on curing time in threaded joints?

The type of metal (activity), temperature, and gap size. These are the factors that most often determine how quickly the joint reaches usable stability.

Medium or high strength – how should this be understood in practice?

It refers to the level of resistance to self-loosening and the force needed for possible disassembly. The choice depends on loads, vibration, and service requirements of the joint.

Are anaerobic adhesives intended for bonding plastics?

These solutions are designed mainly for metal-to-metal joints. In mixed applications (metal + plastic), plastics do not catalyse curing like metal does, so such uses require careful product selection.