Change in tightening torque when using Corrsion Inhibitor?


#1

I came across this thing called Corrosion Stop made by Fabulous Blaster company. I am thinking it’s similar to Boeshield T-9 Waterproof Lubricant. Other companies make similar stuff also. It sprays bubbly petroleum stuff, and it dries leaving a thin film of what looks like wax.

According to the label, its uses includes lug nuts. I have been having problem with rusting lug nuts. So much so that I broke one off last spring when I was changing over to summer tires from winter tires. I wrote to Blaster company asking whether I should adjust tightening torque when I spray their corrosion stop stuff. Their answer is that I need not adjust tightening torque.

Does that make sense? Boeshield calls its product waterproof LUBRICANT, which should mean I should be lowering the tightening torque, if I use that stuff on lug nuts. I just want some opinion from other people.

Thank you.


#2

Personally, I wouldn’t use anything like that on my lugnuts. Instead, if they’re getting stuck, I’d just break them and retorque them once a month or so, which should only take ten minutes at most.


#3

Never heard of the stuff and certainly would never use it on lug nuts.


#4

Many people have safely used anti-seize compound on lug nuts. You just need to be careful and know what you’re doing. There’s an in-depth discussion of the subject here:

https://www.engineersedge.com/wwwboard/posts/13070.html

Anti-seize compounds and lubricants will increase bolt tensile stress induced by a give torque. For a copper-graphite anti-seize, you should apply only about 75% of the specified dry torque to obtain the desired tensile stress in the stud.

If you want to get specific, you can look up your vehicle’s torque spec here:

http://www.discounttire.com/infoCenter/infoWheelTorque.html

And since every project is an excuse to buy a new tool, you could get yourself a torque wrench and use it to torque the lug nuts, applying the appropriate correction factor for whatever compound you apply to the threads. The Handyman-in-Your-Pocket book sold at Ace Hardware has a 2-page table listing correction factors for a variety of lubricants. But as I mentioned above, a typical copper-graphite anti-seize requires only about 75% of the dry torque.

One thing to remember is that if you do use anti-seize, you must not let a mechanic use an air wrench to tighten the nuts, because the anti-seize makes it easier to break a stud by overtorquing. You have to remember to reduce the torque by the appropriate factor, and the average Joe mechanic working on your car will not do that.


#5

Thank you very much for your comments. I initially thought of using anti-seize, but the corrsion stop I bought specifically mentions lug nuts. I thought I’d ask.


#6

The corrosion stop is probably fine. I don’t know what the composition is, though, so it’s impossible to find the exact correction factor for torque. For comparison, WD-40 requires 80% of dry torque. Stuff with more lubricant in it requires in the 50-75% range. To be safe I’d apply 75-80% of the specified dry torque when using Corrosion Stop (despite what they told you, which is almost certainly wrong.)


#7

I won’t service a vehicle where it’s required to remove the wheels/tires, and I find any kind of lubricant on the lug nuts/studs.

These are dry torque fasteners. And adding any kind of coating skews the torque readings. Always too the side of over-torquing. This over-torquing can cause the lug studs to stretch to the point of failure if repeated often enough.

Wheels/tires are constantly removed/reinstalled to do all kinds of service. Tire replacement, tire rotating, brake service, steering/suspension service, among other things.

So each time the the wheels/tires are installed, this hardware is over torqued.

And looking up correction factors for torque is a guessing game.

The way I look at it is, if I’m unable to do the proper dry torque spec, I’m not going to do it all.

I don’t need to have a lug stud snap off because I couldn’t tell if I was torquing at the right spec, and then I end up paying for the broken stud replacement.

Or if the studs fail from over-torquing while the vehicle is being driven. And I get hauled to court and sued for damages/injuries/or death.

Tester


#8

The experts here mostly don’t recommend any lubricants on lug bolts, for the torque reasons described above. They are probably right, and just making sure the lug bolts are clean is he best practice.

That said, I’ve always put a very thin layer of moly on all my vehicle’s lug bolts during wheel servicing – 70’s VW Rabbit, 70’s Ford truck, 90’s Corolla — and never had a lug rust problem or the lugs over-tighten and snap off or the bolts come loose.


#9

What is moly?


#10

I’ve always lubed lug bolts and never had a problem with it.
I have, however, had trouble with UNlubed lug bolts.


#11

Moly is molybdenum disulfide, a very effective lubricant. Depending on the exact form (grease, anti-seize, etc) a molybdenum compound will require a torque multiplier of between 0.45 and 0.70.

George’s experience using moly without ever breaking a stud shows it can be done safely if you’re careful about not overtorquing.


#12

I live in a high rust area. The last time I rotated the tires on my 3 1/2 year old Toyota I had to beat them off with a sledge. The usual kicking inward on the tire would no longer break them loose. They had been on the car about 8 months over the winter. I did not have any trouble with the lugs though, the wheel had rusted to the hub and rotor through a liberal coating of anti-seize.


#13
 <b>you should apply only about 75% of the specified dry torque to obtain the desired tensile stress in the stud</b>

I take some issue with this point. Agreed that the tensile load on any fastener with lubricant on the threads will increase compared to dry. The tensile load on a lug stud, however, is the sum of the thread friction and the lug nut’s seat friction - the wide area in contact with the wheel.

The seat friction is much greater than the thread friction if both are dry. If the threads have lubricant and the seat does not - the correct way of using anti-seize - the tensile load in the stud will only be slightly higher than without anti-seize. IMHO, a 75% lower torque spec would then be too little. Something more like 90% is more appropriate and what I’ve been using for 30 years with virtually no broken or rusted studs.


#14

I did an experiment years ago on my truck, where I torqued a lug-nut onto a cleaned and thread-chased but dry, un-lubed stud to the torque spec, then made marks to note how far it twisted. Then I removed the lug nut, and repeated, but moly’ing the stud first, twisting the nut to the same marks. The torque wrench measurement was indeed slightly less, but rather than 45% to 75%, I found it was more like 85 - 90% of the previous dry torque. It’s sort of an imprecise measurement, but something a person can do to get some kind of judgment on dry vs lube torque differences for their particular application.


#15

I am not worried about over stretching the studs when oiling the threads, if my experience with Toyota dealers, tire shops and inspection stations is any indicator, most people are running around with more than double the specified torque for their lug nuts.