Expert Guide to Anaerobic Adhesives and Threadlockers: Applications, Performance, and Best Practices

When designed into a mechanical assembly, anaerobic adhesives serve as threadlockers, sealants, retaining compounds, and flange sealants. They lower component inventories, cut manufacturing costs, improve equipment reliability, and reduce warranty claims by ensuring robust, long‑lasting bonds.

These adhesives stay liquid until they are isolated from oxygen in the presence of metal ions—such as iron or copper. Once a nut and bolt are mated, the adhesive rapidly cures into a cross‑linked plastic that adheres strongly to many metals, delivering high shear strength in most applications.

• In threaded assemblies, anaerobic adhesives lock the fastener, prevent loosening and corrosion, preserve clamping force, and allow controlled torque removal.

• For rigid cylindrical parts—e.g., attaching a bearing to a shaft—retaining compounds bond components that previously required press or shrink fits.

• Gasket‑forming anaerobic materials create leak‑proof seals between flanges, stopping moisture, gas, fluid, or contaminant leakage.

These compounds set in minutes at room temperature and achieve full cure within 24 hours. Heat can accelerate the process—30 minutes at 120 °C—while primer or activator primers may be applied to the fastener surfaces for rapid bonding. No component mixing is needed.

During cure, polymer chains infiltrate every thread imperfection, increasing friction and filling microscopic gaps. The result is a 100 % unitized assembly that resists lateral movement and protects against corrosion from moisture, gases, or fluids.

A typical nut‑and‑bolt pair has only ~15 % metal‑to‑metal contact. A few drops of threadlocker fill the voids, curing to a thermoset plastic that delivers high torque strength, temperature resistance, rapid cure, easy dispensing, and vibration resilience.

Threadlockers come in low, medium, and high‑strength grades, color‑coded for quick identification: purple/blue (low/medium) and green/red (high). Low and medium grades can be disassembled with hand tools at room temperature; high grades require 450 °F heat for removal.

Fastener size determines the required strength and viscosity: low‑strength lockants suit screws up to ¼″; medium grades cover fasteners up to ¾″; high‑strength lockants are ideal for up to 1″ fasteners in permanent assemblies. Low‑viscosity, penetrating formulations work on pre‑assembled fasteners up to ½″.

Proper wetting of the entire thread engagement area is essential. The adhesive must reach the full thread length, which depends on thread size, adhesive viscosity, and part geometry. For through‑hole assemblies, apply the lockant only where the nut and bolt will meet when tightened; for blind‑hole or cap screws, apply to both the bolt and the hole bottom to prevent air pressure from displacing the adhesive.

Traditional anaerobic adhesives struggled with: 1) curing on contaminated metal or non‑metal surfaces, 2) enduring temperatures above 300 °F, and 3) resisting prolonged mechanical stress. New surface‑insensitive formulations now cure on oily or dirty surfaces and on passive or plated substrates without primers, broadening their applicability.

Modern anaerobic lockants, thanks to advanced chemistry, retain integrity up to 400 °F, making them suitable for automotive and aerospace environments that demand extreme thermal cycling. Toughened variants offer superior performance under high vibration, rotation, shear, and tensile loads, reducing impact sensitivity and enhancing long‑term durability.