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April 23, 2012

Stainless Steel Galling (cold-welding)

From time to time, we get complaints from customers regarding galling of stainless steel fasteners.

Here is an excerpt from the Industrial Fastener Institute’s Standards Book:

Thread galling seems to be the most prevalent with fasteners made of stainless steel, aluminum, titanium and other alloys which self-generate an oxide surface film for corrosion protection.  During fastener tightening, as pressure builds between the contactin and sliding thread surfaces, protective oxides are broken, possibly wiped off and iterface metal high points shear or lock together.  This cumulative clogging-shearing-locking action  causes increasing adhesion.  In the extreme, galling leads to seizing – the actual freezing together of the threads.  If tightening is continued, the fastener can be twisted off or its threads ripped out.

 During minor galling, the fastener can still be removed, but in severe cases  of galling, a strong bond between the bolt and nut can prevent removal of fastners. Unfortunately, little is known on how to control it, but here are two ways to minimize this effect:

Decreasing installation RPM speed will cause less friction and decrease heat generation.

Lubrication used prior to assembly can dramatically reduce or eliminate galling. Recommended lubricants should contain higher amounts of molybdenum disulfide, such as graphite which is very commonly used as a solid lubricant or special anti-galling lubricants sold by chemical companies.

We provide anti-seize compound with all of our antennas and strongly encourage you to use it to reduce the aggravation of galling.  Contrary to popular belief, galling of stainless steel is not a symptom of a “cheap” fastener – it is prevelant in all types of stainless steel, aluminum and titanium fasteners.  You can be assured that the stainless steel fasteners we provide with our products are manufactured of high quality. 

Save yourself a lot of grief and always use a thread lubricant when working with stainless steel fasteners.





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