How to Prevent Galling in Stainless Steel Fasteners

Stainless steel is specified for fastener applications because of its corrosion resistance and durability in harsh environments. But it has one persistent weakness: it galls. Understanding what causes galling stainless steel fasteners, and how to stop it, separates engineers who solve the problem once from those who keep solving it repeatedly.

What Is Galling, and How Is It Different from Seizing?

Galling is a form of adhesive wear caused by friction between metal surfaces under pressure. When a stainless steel fastener is tightened, the threads slide against each other under significant contact force. That friction generates heat, which breaks down the thin oxide layer that forms naturally on stainless steel surfaces. Once the oxide film is gone, the bare metal makes direct contact and begins to bond at a microscopic level. The result is a fastener that effectively cold-welds itself during installation, sometimes mid-tightening.

Thread galling and seizing describe related but distinct problems. Galling refers specifically to the adhesive damage to thread surfaces caused by friction during installation. Seizing describes the condition of a fastener that will not move, which can result from galling but also from corrosion, contamination, or thermal bonding over time. Galling happens during assembly. Seizing is often what you find later when you try to remove hardware that galled during installation.

Why Stainless Steel Fasteners Are Especially Prone to Galling

Most metals develop surface oxide films, but stainless steel’s film is both thin and self-regenerating. That regeneration is what makes stainless steel corrosion-resistant in service. During fastener installation, however, it works against you. As threads slide against each other and the oxide layer is abraded away, stainless steel rebuilds it almost immediately. The repeated cycle of oxide formation and destruction generates additional heat, which accelerates the adhesion process.

Austenitic stainless grades, are the most susceptible. They have higher nickel content, lower hardness compared to other metals, and a strong tendency to work-harden under friction. Work hardening increases localized surface hardness during tightening, raising contact stress at thread surfaces and compounding the adhesion risk.

How to Prevent Galling in Stainless Steel Fasteners

Several well-established methods reduce stainless steel galling risk when applied correctly.

Apply the Right Lubricant or Dry Film Coating

Thread lubrication is the single most effective countermeasure. A lubricant reduces friction at the thread interface and breaks the metal-to-metal contact cycle that initiates galling. Effective options include:

• Nickel-based anti-seize: Rated to approximately 2,400 degrees F. The standard choice for exhaust manifold studs, turbocharger hardware, and any high-temperature stainless fastener application.
• Molybdenum disulfide (moly) coatings: Effective dry film lubricants for moderate to high-temperature applications. Can be factory-applied.
• PTFE-based coatings: Significantly reduce friction coefficient. Particularly useful for fasteners that see repeated removal and reinstallation.
• Graphite-based compounds: Suitable for moderate-temperature applications, but not for exhaust hardware above 850 to 900 degrees F.

Control Installation Speed

Galling risk increases with tightening speed. Faster installation generates more friction heat in a shorter window. Using a calibrated torque wrench rather than an impact gun, and tightening at a controlled rate, gives metal surfaces more time to distribute heat and reduces the thermal spike that triggers adhesion.

Mix Dissimilar Grades Where Possible

Pairing stainless steel fasteners of different alloy grades at the nut-bolt interface reduces galling risk. A 316 stainless bolt running against a 304 nut creates different hardness profiles at the thread contact surface, which interrupts the adhesion mechanism. In high-temperature applications, pairing A286 alloy studs with standard stainless hardware further reduces the risk because the material properties differ significantly.

Inspect and Clean Threads Before Assembly

Dirt, surface burrs, thread damage, or contamination increase friction at contact points and create localized heat concentrations. Any surface imperfection on the thread form is a potential galling initiation site. Clean mating threads and inspect for damage before every assembly, particularly in repair or reuse situations.

Upgrade to A286 or Nickel Superalloys for Critical Applications

When stainless steel galling creates chronic failures in a specific application, material selection is the permanent fix. A286, an iron-nickel-chromium superalloy, is significantly more resistant to galling than standard austenitic stainless grades because it maintains better mechanical properties at elevated temperatures and has improved surface characteristics under friction.

MacLean-Fogg’s Maynard A286 Stainless Steel Studs have been specified by leading OEMs in automotive, heavy duty truck, and industrial engine applications for exactly this reason. MacLean Maynard has been warm-forming specialty alloy fasteners for over 25 years, with process knowledge that most fastener manufacturers cannot replicate.