Thread-locking fluid

Thread-locking fluid or threadlocker is a single-component adhesive, applied to the threads of fasteners such as screws and bolts to prevent loosening, leakage, and corrosion. Most thread-locking formulas are methacrylate-based and rely on the electrochemical activity of a metal substrate to cause polymerization of the fluid. Thread-locking fluid is thixotropic, which allows it to flow well over time, yet still resist shocks and vibrations. It can be permanent or removable; in the latter case, it can be removed with heat, for example. Typically, brands are color-coded to indicate strength and whether they can be removed easily or if they require heat for removal. Thread-locking fluid was developed by American professor Vernon K. Krieble in 1953. His company, American Sealants, founded the Loctite brand. An early version of the compound was patented in 1960. Typically, thread-locking fluids are methacrylate-based, and cure anaerobically. Thread-locking fluid is often a thixotropic fluid: under shear stress, it exhibits a time-dependent decrease in viscosity to allow it to be squeezed into place but not flow too quickly on its own. Thread-locking fluid is typically sold in small containers, in amounts from 5 millilitres (about one teaspoon) to . Threadlocker is also sold in sticks and in tape form, similar to teflon tape. Thread-locking fluid may be applied before or after assembly, depending on the type. Threadlockers are available in varieties of "permanent", "removable", and "low-strength" formulas. Many brands color-code the container and the fluid itself to indicate the degree of permanency. The low-strength types prevent loosening under vibration, but may still be readily disassembled. Removable types resist higher amounts of vibration, but may still be disassembled with hand or power tools. The strongest permanent threadlockers are rated at in shear strength. The applied torque required to loosen a permanently threadlocked fastener may exceed the yield strength of the fastener itself, such that attempting disassembly by force may twist off the stem of the fastener.