Why 316L Parts Seize and What to Use Instead

September 21, 2026

A stainless bolt that turns freely for three threads and then locks solid. A valve stem that works on the bench and seizes in service. A shaft in a bore that comes apart only by being destroyed. All the same failure, and it is not corrosion.

Galling is not wear as most people picture it

Abrasive wear removes material gradually. Galling does something different and faster. Two surfaces in sliding contact carry the load on a small number of high points. Pressure at those points is enormous. The passive oxide film on stainless is only a few nanometres thick, and it breaks. Underneath are two clean metal surfaces pressed together hard, with no oxide between them, and they bond.

Keep sliding and the bond tears. A lump of one face is now stuck to the other. That lump raises the contact pressure further, so the next bond is bigger. Within a few turns the joint has picked up enough material to seize.

The general description of galling is worth reading if the failure is new to you, because the speed of it surprises people who expect wear to take months.

Why austenitic stainless is the worst material for it

Three properties stack up badly.

The passive film is thin and it reforms slowly. The same film that stops corrosion is not a bearing surface.

The material is soft and ductile. Austenitic grades deform rather than resist, so contact points flatten and the true contact area grows.

Stainless work hardens. The galled surface becomes harder than the base metal, so the damage it does on the next pass is worse.

304 and 316L are the classic offenders. A 316L fastener threaded into a 316L nut is one of the most reliably seizing combinations in engineering, which is why experienced assemblers pair stainless fasteners with a different grade or a lubricant.

Where it bites on machined parts

• Threads, especially fine pitch and especially in a blind hole
• Valve stems and seats that cycle
• Shafts in bushings and any close sliding fit
• Bayonet, cam and quick release fittings
• Sanitary clamps and couplings that are opened and closed daily
• Food and pharma equipment where lubricant is not allowed

The last one is the reason this article exists. In a wash down environment you cannot solve galling with grease.

Nitronic 60 and what it actually does

Nitronic 60 is an austenitic stainless with about 4 percent silicon, 8 percent manganese and nitrogen. It is still austenitic, still non magnetic in the annealed state and still corrosion resistant, with a PREN near 19, roughly level with 304.

The silicon and the nitrogen change the surface behaviour. Under contact load the surface work hardens quickly into a form that resists adhesion instead of promoting it, so the local bonds that start a gall do not form the same way. Published galling threshold stress for Nitronic 60 against itself is more than an order of magnitude above 316L against itself.

That is the whole value proposition. Same corrosion class as 304, dramatically better in sliding contact, no lubricant required.

It also has roughly twice the yield strength of 304 in the annealed state, which is a useful bonus on stems and pins.

The cost. It machines poorly. Expect it to behave like 316L or a little worse, with high cutting forces and rapid work hardening under a dull edge. It is also a specialty item, so sourcing takes longer and minimum bar quantities can be awkward on a small job. Say in the RFQ what size you need and accept that stock may drive the lead time.

Cheaper ways out, in the order to try them

1. Use two different grades. Galling needs similar materials. A 316L stem in a bronze or a 17-4 PH bushing is far less prone than 316L on 316L. This is free.
2. Change the hardness. A hardened 440C or 17-4 PH face against a softer austenitic one breaks the symmetry.
3. Improve the finish. A smoother surface carries load on more points at lower pressure. Ra 0.8 micrometre or better helps, and electropolishing helps more because it rounds the peaks rather than just lowering the average.
4. Coat one face. Hard chrome, nitriding on the right grade, or a PTFE based coating.
5. Then reach for Nitronic 60, when the part cycles often, cannot be lubricated and has to stay corrosion resistant.

What to put in the RFQ

Say that the part slides, how often and against what. That one sentence is what lets a shop flag a galling risk before the parts are made rather than after they seize. Give the mating material, the contact pressure if you know it and whether lubricant is permitted.

If you are already committed to Nitronic 60, say so early. Stock availability, not machining, is usually the long pole. The buyer guide covers the rest of what belongs on a stainless drawing, and what to put in a stainless RFQ has the full checklist.

Frequently asked questions

Figures in this guide are published specification limits or published typical values for the alloy, not measurements of any part. Machinability is rated against free-machining carbon steel B1112 at 100 and PREN is chromium plus 3.3 times molybdenum plus 16 times nitrogen. The conventions are set out in thereference section and the editorial standards.

Keep reading

• When to Machine 17-4 PH and When to Age It
• Duplex 2205 and the Parts That Actually Need It