Threadlockers are anaerobic adhesives engineered to prevent nuts, bolts, and other threaded fasteners from loosening under vibration, shock, or thermal cycling. Unlike conformal coatings or structural adhesives, they cure only in the absence of oxygen and in the presence of metal ions, meaning the liquid resin remains stable and workable while exposed to air, then polymerizes into a hard, thermoset plastic once confined between the mating threads of a fastener.
Threadlockers are graded by their locking strength: low-strength grades allow the fastener to be removed with standard hand tools for parts requiring periodic adjustment or maintenance, medium-strength grades balance secure retention with serviceability for general assembly, and high-strength grades create a permanent bond intended for fasteners that should never be removed. Selection depends on the required breakaway torque, the fastener size and metal type, and whether future disassembly is expected.
