Why Do Stainless Steel Bolts and Nuts Tend to Seize Up When Tightened?

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Why Do Stainless Steel Bolts and Nuts Tend to Seize Up When Tightened?

Last updated on Jan 05, 2026

Many applications require fasteners to be rust-resistant. Besides using surface treatments for corrosion protection (Further Reading: Characteristics and Selection of Different Surface Rust Prevention Measures), stainless steel fasteners are also an excellent choice.

However, many professionals have encountered seizing (also known as "galling," "adhesion," or "cold welding") when tightening stainless steel bolts and nuts. What causes this phenomenon?

We know stainless steel resists rust thanks to a chromium oxide film on its surface (Further Reading: Why Does Stainless Steel Still Rust?). During bolt tightening, the high pressure (up to hundreds of megapascals) and frictional heat (local temperatures can exceed 300°C) generated by thread engagement damage this oxide film, exposing the highly reactive "raw" metal surface underneath.

Without the protective oxide layer, the bare metal surfaces come into direct contact. Stainless steel not only has a high coefficient of friction but also very low thermal conductivity (typically one-third that of carbon steel), meaning heat is easily generated but cannot dissipate quickly.

The thread teeth soften at high temperatures, undergo shear and adhesion during tightening, and form cold welds. As tightening continues, the bonded areas of the threads tear, producing tiny metal particles. These particles clog the thread path, leading to greater friction, heat, and pressure—a vicious cycle that can cause the nut and bolt to seize in a short time.

The risk of seizing is heightened if any of the following factors exist during tightening: poor thread alignment (tilted installation), foreign objects on the thread surface (such as weld spatter or metal shavings), rough thread surfaces, excessive tightening force, or overly fast tightening speed.

When thread adhesion and seizing occur, the required tightening torque increases. Using the specified torque will no longer generate effective preload. This issue is hard to identify during tightening and invisible from the outside. After seizing, the bolt/nut won’t loosen, but the joint may suffer fatigue failure under load due to insufficient preload.

So how to prevent seizing of stainless steel threads?

First, clean and inspect the threads. Ensure both the bolt and nut threads are clean, free of dirt, metal particles, and other debris. Rough or damaged threads increase friction and the risk of galling.

Second, lubricate the threads. Apply wax-based, nickel-based, or PTFE (polytetrafluoroethylene)-based anti-seize lubricants. This reduces friction and is one of the most effective ways to prevent galling. Some manufacturers recommend copper-based or graphite-based lubricants, but special care is needed. For example, copper-based anti-seize agents can cause electrochemical corrosion in certain environments; at high temperatures, graphite may react with chromium to form chromium carbide at grain boundaries, reducing the stainless steel’s corrosion resistance.

Finally, use appropriate tools and control the speed during tightening. When installing, use a torque wrench or manual socket wrench to assemble stainless steel fasteners slowly. Avoid high-speed power tools, as excessive tightening speed can cause heat buildup at the thread interface and increase the risk of galling.

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Why Do Stainless Steel Bolts and Nuts Tend to Seize Up When Tightened?