Anaerobic Threadlocker - Which Strength Do You Need?

How does an anaerobic threadlocker work?

Anaerobic adhesives are single-component liquids that cure under two conditions: absence of air and contact with metal ions. Both are present in the thread gap between screw and nut, so the adhesive polymerises there into a tough plastic that fills the thread flanks form-fit.

The cured film stops micro-movement and self-loosening from vibration, seals against moisture and protects the thread against corrosion and fretting. As long as air can reach the product, for instance in the bottle or on an open surface, it stays liquid.

Low, medium or high strength - which grade?

The strength grade sets the later breakaway torque and therefore how removable the joint is. Choose the grade by the requirement: will the screw be undone regularly, only during repair, or should it stay permanently secured?

Low-strength products are often purple and ideal for small threads and adjusting screws. Medium-strength are usually blue and the universal standard for most fasteners. High-strength are typically red, fill larger gaps and can normally only be released after heating to about 250 °C.

How do I choose by thread size and gap?

Besides strength, the choice depends on thread size and gap fill. Low and medium viscosity products wick into tight fine threads, while thick or paste types fill large gaps and do not drip during overhead assembly.

• Small threads M2 to M6: low to medium strength, thin liquid for good capillary action.
• Medium threads M6 to M20: medium strength as the universal standard.
• Large threads from M20: high strength and higher viscosity for wider gaps.
• Overhead or vertical work: choose a paste or gel version to prevent run-off.
• Always apply to a clean, degreased and dry thread.
• Check the temperature limit: standard up to about 150 °C, special types to 200 °C.

Frequently asked questions