rust and penetrating oils

[gww]

Subject: rust

Machinist's Workshop magazine recently published some information on
various penetrating oils that I found very interesting. Some of you
might appreciate this. The magazine reports they tested penetrates for
break out torque on rusted nuts. They are below, as forwarded by an
ex-student and professional machinist. They arranged a subjective test
of all the popular penetrates with the control being the torque required
to remove the nut from a "scientifically rusted" environment.

*Penetrating oils ........... Average torque load to loosen*
No Oil used ................... 516 pounds
WD-40 ..................... ... 238 pounds
PB Blaster .................... 214 pounds
Liquid Wrench ...............127 pounds
Kano Kroil .................... 106 pounds
ATF*-Acetone mix. ...........53 pounds

The ATF-Acetone mix is a "home brew" mix of 50 - 50 automatic
transmission fluid and acetone. Note this "home brew" released bolts
better than any commercial product in this one particular test. Our
local machinist group mixed up a batch and we all now use it with
equally good results. Note also that "Liquid Wrench" is almost as good
as "Kroil" for about 20% of the price. Steve from Godwin-Singer says
that ATF-Acetone mix is best, but you can also use ATF and lacquer
thinner in a 50-50 mix.

*ATF=Automatic Transmission Fluid

[koanes]

Thanks for throwing that out there Gary. I have been using Kroil for many years, but prior to that my favorite was Mouse Milk. I don't know if MM is still available, the only source I ever had was an old time salesman that stopped at the shop a couple of times a year. Good to know I can mix my own penetrating lube at a fraction of the cost of AeroKroil.

[BoschZEV]

Machinist's Workshop magazine recently published some information on various penetrating oils that I found very interesting...

This "study" has been copied many places on the web since the magazine published it in 2007. Unfortunately, the author's attempt to "scientifically rust" and then reproducibly measure the torque required to loosen the bolts is seriously flawed by the artificial rusting technique he used, the small number of test bolts use used (3), and the averaging to produce the table. At very best, the only thing that might be inferred from the study is that oil of some kind is better than no oil.

I have a large quantity of Sili-Kroil ("The oil that creeps, plus silicone") so it is the one I always use. But, in no way have I done a study of penetrating oils myself. All I can say about it is that in a half-dozen or so side-by-side comparisons I've done over the past 20 years of similarly rusted fasteners in the same component, Sili-Kroil definitely works a lot better than having used no penetrating oil at all.

[c.o.]

I've used Liquid Wrench on some rusted nuts on a 99 year old Harley engine with no luck. I will admit though that I couldn't bring myself to try anything near 127 pounds!!! Interesting thread Gary.. thanks for starting the discussion.

[exeric]

Perhaps my favorite part of messing with rusty old contraptions, is getting them apart and the challenges associated with that. I have to say that from my empirical observations, oil is rarely the primary source of success in getting a badly rusted assembly apart. However, as BoschZEV said, 'oil works better than no oil.' In my experience, you better have access to heat, every wrench known to man, hammers, a milling machine, a lathe, and understanding neighbors that don't call the police when they hear screaming profanities. Lately, I've been using beeswax as a penetrant, as I've heard more than one old timer recommend it. It works okay, but I wouldn't say it's a miracle lubricant. When I have looked at the threads of a stubborn assembly that I've used beeswax on; I can see that the beeswax did get there. Also, heat is the vehicle that makes it viscous, and unlike petroleum based penetrants, beeswax doesn't burn off. Still, no oil is going to substitute for resolute determination, muscle, and the will to get some rusty piece of crap apart.

[BoschZEV]

To be effective a penetrating oil needs three properties. The first is a combination of low surface tension and high adhesion to the rust, in order to maximize the capillary force drawing the oil into the microscopic channels in the rust. The second is low viscosity, in order for the oil to be able to insinuate itself through the channels in the rust as rapidly as possible. The third is chemical reactivity with the rust itself. Even if all the channels are rapidly filled with oil, at that point you are still no better off than before, since what is holding the rusty bolt in place are the iron oxide connections between it and the housing where there are no channels, i.e. where oil could not penetrate. Whether the voids between the rust are filled with air or with oil makes no difference to the binding strength of the rust.

The surface area of the rust gives the bolt an effective surface area very much larger than the simple geometrical area of the threads so even though the strength of the rust is less than that of steel (say, 10x less, to make up a number), the total binding force is very much greater (if the surface area is 100x larger, which again is a made up number, but a perfectly reasonable one, then the holding force is 1/10 x 100 = 10x greater). Once the fastener can move slightly the lubrication from the oil will be able to do good, so what is needed is an additive in the oil that chemically dissolves the rust.

The reason heat in combination with a penetrating oil works is the differential thermal expansion/contraction between the housing and the bolt alters the microscopic landscape ever so slightly, opening up new voids that now can fill with penetrating oil, and closing up old ones that already have penetrating oil in them so they are left with a low friction lubrication layer.

[Chris Haynes]

I love AeroKroil. I buy it by the case.

[T. Cotten]

I did too, Chris!

But the last case of spray cans all have faulty nozzles, and customers brought them all back.
(And too late for me to complain to Kano....)

Now I have a lifetime supply in bottles with an eyedropper, and a wall display of the rest of the case.

Lesson: Buy it in the jug.

....Cotten

[BoschZEV]

Now I have a lifetime supply...

Even though I have a lifetime supply of Silikroil I just checked to remind myself of the differences:

Kroil -- their penetrating oil
AeroKroil -- the identical Kroil, but in an aerosol can
SiliKroil -- the identical Kroil with the addition of dimethyl silicone, claimed to have longer protection against additional rust

So, as far as your rusty nuts are concerned, all three should be functionally identical.

[Rodger Brandstatter]

A few years ago, I was looking for a product to clean antique motorcycle sheet metal with, in lieu of using any water on these usually rusted parts. I ran into the Strong Arm Spray guy at the Davenport meet. After a brief demonstration, I bought a can to try. Since then, I have been buying it by the case. It never ceases to amaze me how easily things will come apart a few minutes after using. I am in the plumbing and heating business, and keep a can in my toolbox at all times. I use it on everything from rusted boiler fittings to corroded trap connections under the kitchen sink. It probably isn't the best method for getting something apart that would take months of reapplication and tapping with a hammer, but for everyday use it's great. As far as cleaning parts goes, it works well and gives the metal a natural patina (it does the same thing for cleaning antiques made of wood). On motorcycle restoration, I like to use it in conjunction with rethreaders (not taps and dies). I use drop or two on the bolt or threaded hole and run the rethreader the clean up and lubricate all the threads on all the bikes I work on. This may sound like an infomercial, but for the kind of work I do, I have never found anything like it.

[jim d]

How long is the ATF and the acetone or lacquer going to be effective when both of these items evaporate very quickly. I would also think the the flashpoint would be much lower with these than Kroil when dealing with the fumes and adding heat to the mix. But I may be missing something.
Jim D.

[DanM]

Jim d-[ you are right- I made up this mix to try to get spokes and nipples apart. After a few days, you only have ATF. I learned to add the acetone to the jar each day and kept applying. I normally use Kroil, (and have gotten some terrible things apart with it) and came to these particularly stubborn spokes, and decided to try the Acetone/ATF. In this single case it did not perform any miracles for me!

When I use the Kroil, I can see the corrosion break down- its in the run off, or if i soak parts in a jar, its in the bottom of the jar. I did not see this occur with the ATF mix.

Dan

[Coolbreeze]

I have given up on Liquid Wrench. Instead of throwing it away, I found a new use: it makes a decent cutting oil when I am machining steel.

[sirhrmechanic]

BTW, we've been playing with a new method for extracting studs, etc. and so far it is working brilliantly. Still use penetrating oil, but we have set up a little vibrator on the end of the stud. (No, it's not pink)... it's basically a diode that runs at high frequency. Available off eBay for peanuts. The vibrator can sit for days as necessary. When we go to extract the studs, they come right out. The combination of penetrating oil and high-frequency vibration is amazing. More to follow. Right now, we've only used it a half-dozen times. But it is showing great promise.

If someone has more time to try it on a more 'scientific' level, input appreciated.

Cheers,

Sirhr

[ricmoran]

CarWell CP-90. It's an ultra thin film inhibitor which penetrates rust and scale. The only failure encountered in use and selling the product over 20 years was a 10-32 stainless set screw that is used to hold the visor shields on aluminum traffic lights as well as cross walk assemblies where the hand lights up with timer.

I've had 1", 1-1/4" and 1-1/2" fasteners that were left in a 55 gallon drum, filled near the top, the drum filled with 4.5 pH rain water and sat over the years. The drum did not have drainage holes punched in it.

The drum sat in various wet filled stages in the tropical heat of day and cool beach side evenings.

The fasteners are used to put concrete forms together and another project was coming up where these were needed.

When we tried to get them to work straight from the drum, total failure as the assemblies were frozen in place and heavily scaled. Sprayed the drum from the top down twice then let it sit for a couple of days. The first 6" - 8" layer of fasteners in the drum came apart without issue, other than a vice and crescent wrench.

Surfaces where the product did not migrate to had to be treated, but all fasteners were used

Used on exhaust studs on my 89 Sportster. After 10 or 12 years of age and misuse with the bike, removing one exhaust stud had it break off in
the head. Treated the other studs to remove them as they all had been butchered over the years from several ex pipe change outs.

Treated the remaining three, then ate a plate of spaghetti and went back to work removing the remaining studs to replace them without a hitch.

The product migrates better than anything I've ever seen and we are advised this by several end users, including fed, state and county governments repair shops.

This product works well to refresh old paint machines without hurting the paint and parkerized parts love the bath with it.

This product can be painted over as well as body fillers stick to surfaces treated with it. of course, sensible surface prep is done prior, such as tack rag or prep solvent.