Why Stainless Steel Heavy Hex Bolts Tend To Seize

Some contractors and assemblers complain about stainless steel heavy hex bolts seizing during the tightening process. This happens with other stainless steel bolts as well, although galvanized heavy hex bolts do not seem to have the same problems. Frequent seizing is often a result of galling, which is common when using stainless steel threaded fasteners.

What Is Galling?

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Galling is often referred to as cold welding. In the case of stainless steel fasteners, it occurs when oxidized film from the stainless steel is broken or wiped away by pressure. During the tightening process, high levels of pressure actually remove that film on the threads of both the bolt and the nut.
When the bare metal meets, it will shear or cold weld together. As you tighten further, the weld strengthens and eventually the fastener seizes. Continued tightening will result in irreparable damage to the threads.

How To Prevent Stainless Steel Heavy Hex Bolts From Seizing

Stainless steel heavy hex bolts present a variety of advantages to many different applications. The tendency to seize is one of few deterrents, and it can be overcome with a little care during the tightening process.
Instruct the assemblers to use a lower RPM when tightening stainless steel bolts. The higher the RPM applied, the hotter conditions become in the area. Galling is more likely in these conditions. While lower RPM levels may lengthen the assembly time, with fewer incidents of seizing the overall assembly will go quicker.
Some manufacturers suggest using an anti-galling lubricant to eliminate the problem. There are various lubricants available, depending on the application. Avoid using chemical-based lubricants in food-related applications, where stainless steel is commonly appreciated for its corrosion resistance and durability. Some lubricants are applied before the bolt is inserted, while others can be applied during the assembly as needed.
Other manufacturers recommend using another combination of nut and heavy hex bolt. Although using nuts made from aluminum bronze will reduce or eliminate the chance of galling, it will also increase the likelihood of corrosion, thereby eliminating one of the major advantages of using stainless steel.
You will need to choose the method that best suits your application, in order to avoid the issue of stainless steel heavy hex bolts seizing during the tightening process.