Anaerobic threadlockers – Permabond
Anaerobic threadlockers are anaerobic adhesives designed to lock fasteners in place. Their role is to prevent loosening due to vibration, thermal expansion or other stresses. Anaerobic threadlockers are also designed to permit safe removal of the fastener. Strange as this may seem at first glance, the most important need is to protect the fastener against damage during the removal process.
The big issue when removing fasteners is torque. One of the key benefits of threadlockers is that they maintain a controlled off torque strength. This makes their performance consistent with the performance demands on the fastener. Torque strength is listed as both “break” and “prevail”. The break (or break away) is the measure of force needed to initiate movement of an unseated fastener in a loosening direction. The prevail (or prevailing torque) is the measurement of average force needed to provide continuing movement, after break away, through first full turn.
Important: Keep in mind that this is the strength of the threadlocker alone. The test is performed on hand tightened unseated bolts.
There are potentially major risks when removing fasteners. Rust, galvanic corrosion and crevice corrosion can weaken fasteners as well as make them very difficult to remove. Surface corruption and sticking issues like these around the thread can do significant damage. Anaerobic threadlockers prevent corrosion so the torque required to remove the fastener is consistent and the risks of applying torque forces that may damage the fastener (and the thread, in some cases) are avoided.
To determine the best anaerobic threadlocker for a fastener that is designed to be removed:
- First determine what the metals are – and note that torque strengths are generally listed on steel. Strengths on passivated metals and anodized aluminum may be less and strength on more active metals such as copper may be higher.
- The size of the bolt also contributes to the strength. Larger diameter fasteners have more surface area and thus more torque is required to remove. Smaller diameters have less surface area but the fastener may not be able withstand as much torque. Be particularly careful with this aspect of selecting your threadlocker. If in doubt consult with the supplier for options.
Removing permanent threadlockers
If a permanent threadlocker is used on a bolt that later needs to be removed, heat the part carefully with a hot air gun at temperatures from 450 to 600°F prior to removing with a wrench. Anaerobic threadlockers cure to a thermoset plastic that will soften at higher temperatures. Once the part is heated, disassemble while still at high temperature. Be patient during the removal of the fastener, and do not apply excessive force if it sticks.
Important: Once the assembly cools down it will re-solidify. Fastener removal should only be conducted under the optimum conditions, to ensure that the threadlocker is able to be disengaged smoothly.
Please note: This information is intended as a general guide only to threadlocker removal, and it is very strongly advised that due care and caution are exercised during the removal process to avoid any damage to fasteners.