What is Stainless ‘galling’?
Galling is when two threads bind together and seize. This seizing or ‘cold-welding’ happens as a molecular level and is common among metal mating surfaces with an oxide layer – like stainless steel. It can result in fasteners having to be cut away as un-threading is impossible.
When is galling on a stainless steel fastener likely to occur?
- With larger threads of stainless fasteners, say M10 and up. This is because of a greater surface contact area, therefore more friction occurs in installation, causing heat and binding.
- Nyloc Locking Nuts – the nyloc causes pressure between the threads, again causing friction.
- When the thread is under load such as a turnbuckle for tensioning wire.
- If there is dirt in the threads.
- Installing too quickly with tooling set at too high a speed.
- When the mating surfaces are of a similar hardness – i.e. a bolt and nut.
How do I prevent galling?
- Lubricate the threads. All stainless steel threads should be lubricated – ideally with a Nickel based lubricant such as Loctite 771 or PTFE based lubricant such as Tef Gel designed for use with stainless steel fasteners. A Lanolin based lubricant such as Lanotec is also suitable and also helps prevent corrosion.
- Remove particles and dirt from threads.
- Moderate the installation speed to a low rate of RPM. If the threads are lubricated, you may be able to install at a higher RPM.
Our best lubricants are found below. Check them out to ensure your threads don't gall!
Good luck with your threading.
For more information on galling, please see this article by ASSDA - Galling by the Australian Stainless Steel Development Association.
NB: This information is provided as a guide only and Anzor does not accept liability for the application of this information. For advice about stainless steel contact the Nickel Institute.