Stainless steel bolt galling explained

[Food Scientist]

Can't take any credit for writing this but thought it was an excellent explanation of what galling is on stainless steel bolts and the importance of using anti-seize.

Galling is one the most common problems when tightening fasteners. Also known as cold welding, galling results in damaged threads, broken fasteners, weakened joints and seized bolts. Essentially, to define galling - it's a form of severe adhesive wear.

Galling happens during installation to fasteners made of alloys such as stainless steel, aluminum and titanium. While the fastener is being tightened, pressure builds between the thread surfaces and breaks down the protective oxide coatings. Without the oxide coating, the thread's metal high points are exposed to each other. This, in turn, creates friction, which causes heat the seizes the metal.

Prevention: Anti Seize lubricant must be applied to the threads of each bolt to installation of the corresponding nut.

 

[wwillson]

calling @Kestas being a highly experienced metallurgist.

 

[E150GT]

I have been thinking of this lately. I am swapping parts from a lawnmower deck from the old to the new. Lots of rusty fasteners. Was thinking of using stainless steel hardware but galling looks to be an issue. Might just use the steel fasteners with anti seize just to avoid that issue.

 

[Cujet]

I use stainless structural screws on my Cessna's non structural wing access panels. They are more precise and stronger than the alternative SS non structural. But they gall instantly. Dipping them in Corrosion X or Corrosion X Max Wax before running them in works wonders. The Max Wax holds up all year and they are no trouble during removal.

 

[wings&wheels]

I use stainless structural screws on my Cessna's non structural wing access panels. They are more precise and stronger than the alternative SS non structural. But they gall instantly. Dipping them in Corrosion X or Corrosion X Max Wax before running them in works wonders. The Max Wax holds up all year and they are no trouble during removal.

I did the same, plain SS on access panels, etc. and structural SS on the tanks. Sill $, but no more rust runs We applied Boeshield prior to install.

 

[BrendanC]

i install stainless hardware everytime regardless of use unless it’s something that needs grade 8 strength. always lube the threads with oil or grease prior to tightening them up. trick is to run them in slowly before torquing. the heat from running them down quickly with power tools will get you in trouble.

 

[Cujet]

I did the same, plain SS on access panels, etc. and structural SS on the tanks. Sill $, but no more rust runs We applied Boeshield prior to install.

Just an FYI, Boeshield works well internally and very well on Stainless Steel screws. However, we don't have good results with Boeshield when used externally. As it tends to sublimate on it's own, flake if thick and simply disappear. Corrosion X Max Wax is a more robust product. As is AV30.

 

[Kestas]

It is true that antiseize is recommended anywhere a fastener is used involving aluminum or stainless steel. Galling is real for these situations. Any experienced mechanic will attest to this, including many in our membership.

 

[thescreensavers]

While ago at work we were assembling some pillow blocks. We had ordered I think it was 3/4" stainless nylock nuts and bolts. It was getting late so we just loosly assembled everything and just put a few turns into the nylock.

Well next morning we couldn't turn anything, even brought in my M18 fuel the following day and that did nothing! We had to cut off 8 nuts.....

 

[CleanSump]

When using a torque wrench with antiseize, lube, or wax, remember to compensate for the lube's affect. Also some aluminum screws/bolts that go into titanium call for torque value plus 45deg or 90deg turn. I don't lube or antiseize those because they are easy to twist off when the friction is reduced, i.e. BMW transmission pan screws.

 

[billt460]

The Nickel used in Stainless Steel alloys is very "gummy" by its metallic nature. And it lends itself to galling far easier than carbon steel. In firearms this is very prone to happen to Stainless Steel auto pistols on the slide and frame rails. The greater the Nickel content of the alloy, the greater chance of this condition occurring.

Especially when the weapon is new. I've seen several Stainless slides literally weld themselves to the mating Stainless Steel frames. The only cure is to heavily lubricate both the slide and the frame with a high viscosity oil. Or oil / grease mixture.

The tighter the fit, the more prone this is to happen. So it is essential that when a Stainless Steel auto pistol is in the process of digesting the first 500 / 1,000 rounds of ammunition at the start of its life, it is very important that these mating surfaces be kept generously lubricated.

This condition is much less of an issue with carbon steel guns, or Stainless slide, blued frame "2 tone" auto pistols.

 

[midobo]

The Nickel used in Stainless Steel alloys is very "gummy" by its metallic nature. And it lends itself to galling far easier than carbon steel. In firearms this is very prone to happen to Stainless Steel auto pistols on the slide and frame rails. The greater the Nickel content of the alloy, the greater chance of this condition occurring.

Especially when the weapon is new. I've seen several Stainless slides literally weld themselves to the mating Stainless Steel frames. The only cure is to heavily lubricate both the slide and the frame with a high viscosity oil. Or oil / grease mixture.

The tighter the fit, the more prone this is to happen. So it is essential that when a Stainless Steel auto pistol is in the process of digesting the first 500 / 1,000 rounds of ammunition at the start of its life, it is very important that these mating surfaces be kept generously lubricated.

This condition is much less of an issue with carbon steel guns, or Stainless slide, blued frame "2 tone" auto pistols.

Nickel and nickel based alloys (UNS N05500 for example) are considered non-galling. The abrasive nature during machining doesn't translate to galling in real life.
For the life of me I can't find the paper, but years ago, maybe 20, I read some research that indicated galling in stainless steel was related to precipitation of chromium carbide at the grain boundaries. But I might been thinking of something else. If I ever find it, I'll post a link.
As we see in UNS S21800, the addition of alloying elements such as silicon and manganese can greatly reduce the propensity of galling in austenitic stainless steels.

 

[oilboy123]

I did marine mechanic work for years. Using stainless fasteners with silicone to seal could be challenging. You had to be very careful.