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?

1. 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.
2. Remove particles and dirt from threads.
3. 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!

Tef-gel	Lanotec

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.