How to Identify and Prevent Galling on Stainless Fasteners
By Mutual Screw & Supply | Published: 2026-10-17
Category: How-to Guides
Learn to spot galling on 316 stainless fasteners, understand the causes, and apply practical prevention methods like lubrication and speed control.
Quick answer
Galling is a cold-welding seizure that occurs between stainless steel threads under pressure and friction. To prevent it, use a high-pressure lubricant, drive at a slow and steady speed, and avoid reusing fasteners that show any sign of thread pickup.
What Galling Looks Like on Stainless Fasteners
Galling appears as torn, smeared, or galled metal on the male or female threads. You may see a rough, silvery patch where material has transferred from one thread to the other. In severe cases, the bolt seizes completely and cannot be turned further or removed without breaking.
Why 316 Stainless Steel Is Prone to Galling
316 stainless steel contains molybdenum for added corrosion resistance, but its austenitic structure is softer and more ductile than carbon steel. Under high clamping loads, the oxide layer that normally protects the surface can rupture, allowing metal-to-metal contact. This triggers cold welding, where microscopic high points fuse and tear apart as you turn the fastener.
How to Prevent Galling During Installation
Apply a thread lubricant containing molybdenum disulfide or copper anti-seize to reduce friction. Drive the fastener at a consistent, moderate speed—avoid power tools that generate heat. Keep threads clean and free of debris. For critical assemblies, consider using a coated or waxed stainless fastener to add a barrier layer between threads.
What to Do If Galling Starts
Stop turning immediately. Back the fastener out slowly if possible. Inspect both the bolt and the mating thread for damage. If you see transferred metal or rough spots, discard the bolt and clean the female thread with a tap. Re-lubricate before attempting a new fastener. Never force a galled bolt—it can break off and require extraction.
Galling Diagnosis at a Glance
- Symptom: Bolt becomes hard to turn, then seizes. Visible torn or smeared metal on threads. Stop immediately—do not force.
- Likely Cause: High friction between 316 stainless threads without lubrication, often combined with fast driving speed or debris. Check your installation process for these factors.
- Corrective Action: Back out the bolt, clean threads, apply anti-seize lubricant, and install a new fastener at slow speed. Replace the bolt—never reuse a galled one.
- Stop / Choose Another Option: If galling recurs on the same joint, consider switching to a coated stainless fastener or a different material like silicon bronze or galvanized steel. Change the fastener type or coating to solve the root cause.
Fasteners That Help Reduce Galling Risk
- M20-2.5 X 60mm Socket Cap Screws | Flat Head Hex Socket Drive | Fully Threaded | 316 Stainless Steel (10 / Pkg.): These M20-2.5 x 60mm socket cap screws are manufactured from 316 Stainless Steel, featuring a hex socket drive. 316 stainless offers excellent corrosion resistance but requires careful installation to avoid galling. Using a lubricant and proper speed is essential with this material.
- M6-1 X 70mm Socket Cap Screws | Hex Socket Drive | Fully Threaded | 316 Stainless Steel (100 / Pkg.): These M6-1 x 70mm socket cap screws are manufactured from 316 Stainless Steel, featuring a hex socket drive. Smaller metric sizes like M6 are especially prone to galling because the thread engagement area is smaller. Lubrication and slow driving are critical for these fasteners.
