Stainless Steel Nuts / Bolts Seizing

I may be mistaken, but if you are using 304 CRES, you will get thread galling. I think using 304L CRES will stop galling. Another solution might be to use silicon bronze or copper nickel, both of which are used for underwater applications. Most important is to use a bolting material that is close to the pipe material in the galvanic series of metals. Actually you are better off using the same metal as the pipe for the fastener; No galvanic problem.

I'm sure anti-sieze is just fine, but check to see if it is waterproof. Consider teflon pipe joint compound, it's probably water resistant, and has teflon, which should last forever.

A word of caution though, do not use the never seize that has copper in its compound in stainless steel into Aluminium castings as the copper in the presence of moisture will devour the threaded hole like a starving man at a barbecue.

True.. metal to metal, SS fasteners do seize, it's an old story. Most colleagues I know use anti-seize compounds, some use brass nuts, some use regular, coated steel nuts with anti seize. Works very well. Even when they corrode, (which takes a very long time) they still turn on a stainless st. (SS) bolt. This is what I did in my "active" years. Never had a problem. Hope this helps.

The technical term is "galling"

http://en.wikipedia.org/wiki/Galling

I have used Tef Gel for quite a few years and am very impressed with the outcome. Don't know about 80 years, but I've seen the results after 20 or so and have no complaints. It was developed for the marine industry and is used by the US government.

Tef Gel is much easier to use than tape or ribbon and has equal longevity in application.

Does the underground pipe

• require to be bolted?
• require to be metallic - could plastics be used instead?

If the bolting is suspect over the long-term, what about the pipe walls?

Bolting is required in some instances. Cast iron fittings form the interface for fire hydrants and other pieces that require a degree of mechanical robustness that is not available in the plastics.

Some items are fitted underneath roads with insufficient cover and are thus mechanical load bearing.

Plastic is becoming the material of choice, but there are also multiple plastics available. Some of our locations it's still more economic to use ductile iron pipe and fittings. The siderial pressure changes are sometimes greater than 20m of head and cycling plastic through that has its own issues.

The "Silicon Valley" solution to this stainless steel fastener galling problem is Nitronic 60 stainless steel. I'm personally proud to have been an instrument in that solution. The current implementation involves the use of Nitronic 60 helicoils. However, the original use in our area goes back to the late 1980's when special Nitronic 60 female threaded inserts were implemented on 14" disc drive rotor disc clamps in conjunction with A286 male threaded bolts. Cleanliness requirements meant that thread lubricants were not allowed.

I don't know of any broadly available Nitronic 60 fasteners other than the helicoils I mentioned above. My opinion is that the best generally available fastener combination would use A 286 aircraft grade screws or bolts. This approach likely does not offer practical replacement hardware for piping flanges. So the next best is conventional 304 or 316 stainless steel with whatever sealant/lubricant looks best.

One thing to consider is that any assembly method that can keep corrosive agents, liquids especially, out of the threads will help prolong the time during which easy disassemble is possible.

Ed Weldon

I have seen stainless compression type fittings for tubing with the nut silver plated on the inside to prevent galling

Hello,

Have you tried using an asphalt based paint to coat all of the surfaces of the dissimilar metals that are coming in contact with one another?

Generally, a liberal application of that material is what I require a Contractor to utilize on steel T-Bolts on Ductile Iron water main retainer glands, and on SS bolts, washers and hex nuts at any valve or special device connection. Just for the heck of it, after the GC has made the final tightening of bolts and nuts, I always require a second heavier and very liberal coating of the asphaltic or bituminous paint for extra corrosion protection. i do this mostly in the case of presence of acidic soils, in addition to the gall problem.

It's fast, reliable, inexpensive, and easy to apply using a paint brush.

BONUS:

Bituminous based paints are also good for extra corrosion protection of any type of non-ferric-based metal such as aluminum that has a surface that comes into contact with concrete.

BEST (USE NICKLE CASTED NUT BOLDS)

OR

2nd (TRY NICKLE ANTI SEIZE WHICH IS HIGHLY PREFFERED FOR STAINLESS STEEL)

OR

DO YOU TRY HOT DIP GALVANIZED WIDE THREAD NUT BOLTS FOR FASTENING YOU UNDER GROUND PIPES

ALSO LET THEM FOR SALT SPRAY TEST AFTER APPLYING SIEZE, HOT DIP GALVANIZE OR NICKLE CASTED NUT BOLTS.

THANK YOU

IMRAN MUSHTAQ

HERCULES METAL COMPANY LIMITED

HEMETCO@YAHOO.COM

My company builds several hundred heat exchangers of 304L and 316L ss every year for use in wash down applications. They all have bolted bonnets and tube sheets. We use ss bolts with monel nuts, ASME SB164 grade. No galling.

As a general rule we always used a 400 series SS nut with a 300 series bolt to avoid galling problems. Using low carbon stainless may not provide sufficient difference (e.g. 304SS bolt w/ 304LSS nut, or vice versa) as many manufacturers use low carbon versions without labelling them as such, or giving a dual rating (i.e. 304/304L). However, all materials selected must be suitable for the environment as even stainless steel can corrode under certain conditions. As these are below ground connections ensure there are no mineral components in the earth that will affect your choice of materials. Considerations of galvanic corrosion mentioned in other posts must be kept in mind as well.

Cadmium Plating will do the trick.

Cadmium plating is still widely used in some applications such as aerospace fasteners and it remains in military and aviation specs. Cadmium plating has a long list of technical advantages such as excellent corrosion resistance even at relatively low thickness and in salt atmospheres, softness and malleability, freedom from sticky and/or bulky corrosion products, galvanic compatibility with aluminum, freedom from stick-slip thus allowing reliable torqueing of plated threads, non-galling, can be dyed to many colors and clear, has good lubricity and solderability, and works well either as a final finish or as a paint base, to name a few.

As an alternative to cadmium plating, Ivadizing makes a good substitute that is environmently friendly and an acceptable alternative to cadmium plating for the aerospace and automotive industries. Ipsen Ivadizer® plating equipment uses ion vapor deposition to apply a high-performance, dense coating of aluminum with superior adhesion and thickness uniformity. Since the Ivadizer® furnace creates a plasma-assisted coating; it provides excellent throwing power, extending the deposit readily into part cavities. Even temperature-sensitive parts can be coated safely and effectively using the Ivadizing process.

After many trials, the best solution I have found to prevent galling and siezure of SST bolted fasteners, regardless of alloy or combination, is to mechanical zinc plate the nuts. Even with electric or pneumatic nut runners, installing and removing as fast as possible, it's impossible to gall the threads.

The company that I work for does a lot of military work and we use a lot of stainless fasteners. Galling is a major problem, so we treat the threads with antiseize compound when ever it's allowed.

As some of the other posts have said you can use monel fasteners, but be prepared to spend a lot of money for them. I recently priced out some 3/8 - 16 unjc 3a x 1.5" long socket head cap screws. The best price I found was $67.00 ea. You can buy a lot of antiseize for the cost of a single monel screw. And if after 15 to 80 years the fasteners bind, do what we do, snap them off and install a new one.

Thanks for the wonderful responses. I am seeing confirmation of what I suspected and am glad to have these observations and accumulated experiences.

In summary of all your responses, anti seize is the economic "must use" with zinc anti seize having some advantage. Dissimilar grades of material provide resistance to the galling effect and there are some "exotic" options that have associated expense. Plating could also give some benefit. (In our case some of the options presented could not be followed due to environmental restrictions.)

I have determined that the anti seize that we use is a "zinc rich" version, but the metal grade is still unknown to me. I'll investigate that through them for follow up.

Again, thanks all for your advice on this.

I might visit the thread again in the future, but intend to go to lower level review from here on.

As suggested by wingnut, design the fitting to make the fastenings removable by shearing or drilling and replace with new.

One more.... be careful of using copper based anti-seize on stainless/aluminium combinations most will react to bind permanatly. Use nickle compounds. Once the final torque checks ar done degrease the area around the bolt/nuts and coat the entire joint with sealing compound suitable to the environment eg poly- urathane paste or bitumen and fabric to keep all moisture out.

As a former Pipefitter/Steamfitter/welder I have done a lot of installs of fire systems over the 20+ years before I decided to go for my degree. We used plain alloy bolts and nuts with a good anti seize. If my memory serves me right they were to the B7 Specs and we never had a failure.

One side bar, If you really want it to last you should install wood pipe instead. Believe it or not we replaces a water line that had been installed in the mid 1800s and was made of iron strapped wood. The metal was mostly gone but the pipe still held over 50psi pressure and the only reason that the line was being replaced was that it could not handle the volume and they were upgrading the plant, not because of any leaks. The old timers knew more than we sometimes give them credit for.

Just to add on to some of the other comments...

Yes, I would consider this to be galling. I work in the airspace/defense world and have seem this issue several times. From what I can tell, I am not an M&P person though I sometimes play one of TV, stainless is extremely sensitive to galling. Any heat generation exponentially increases the issue. Clean threads (rolled instead of cut, if possible), lubrication, slow application of torque, etc should all be implemented. (Nylon is worse but any friction enhancing locking feature generates heat and should be avoided.) Similar to other comments, I've been told that differentiating the alloys helps as well. (For example, mixing martensitic and austenitic hardware is going to be better then both of the same grain structure.)

You did notice this thread started in early 2010?

Dow/Molykote-1000 anti-seize on 304 or 316 stainless. Or Permatex anti-seize is a similar copper based product. Grainger sells it in 4 oz cans.

Our shop uses this stuff on 304/304L, 316, and C23400 bronze parts for customer assemblies all the time. Application is -200 - -300 degree F environment though, so definitely no water :))

Halocarbon 25-5s synthetic fluoridated grease is commonly used to prevent galling of stainless fasteners in the oxygen/ chlorine gas industry for pipe fittings

Used by military since being developed half a century ago

inert, non-flammable, water proof(hydrophobic- does not mix with water), unaffected by uv, no hydrocarbons to oxidize- infinite life, natural load carrying

Halocarbon 25-5s synthetic fluoridated grease is commonly used to prevent galling of stainless fasteners in the oxygen/ chlorine gas industry for pipe fittings

Used by military since being developed half a century ago

inert, non-flammable, water proof(hydrophobic- does not mix with water), unaffected by uv, no hydrocarbons to oxidize- infinite life, natural load carrying

We used SS bolts and nuts to join 11KV cable plugs and found never seize protected the thread in the nut provided the bolt and nut were not over tensioned for when that happened the threads stretched slightly and the only way to get them apart was to us two big breaker bars and snap the bolt.

Worst offender was the gorilla on the impact gun.