Penetrating Oil/Spray

Absolutely. Some better than others.

See if you can find "Kroil". It's the best penetrant I've found. So good at seeping, that it seeps out the rolled seam in the oil can I put it into.

Good question. Seems to work, altho I understand your doubts.

The real question to me is: are these sprays any better than regular old OIL???

Different types, tho. I always thought the old Liquid Wrench was better than WD 40; there is, I think, a newer liquid wrench; and something semi-nasty, a spray called PBS, I think, which seems pretty powerful, at least smell-wise! The old liquid wrench had very good anti-rust properties, as well. Really just gotta do lotsa rusted nuts, w/, w/o spray, and get a feel for the results. WD 40 supposedly dries to a film.

Some people (some plumbers) swear by Coke--pretty heavy phosphoric acid (H3PO4), pH=2!! Also removes stuck tooth enamel. :)

But here's what ahm looking for: Remember when 3-in-1 came out w/ a *spray oil*? Anyone seen this lately?? A few hardware stores I checked haven't heard of it. Haven't subjected myself to the effing ""mavens"" at Home Despot yet.

They work all right. It seems to me that it may not make much difference which kind you use. It just has to be thin enough, and attracted to the metal enough, to wick into the joint by capillary action. Iron can expand up to seven times it's original volume when it rusts. This is one of the reasons why a rusted joint gets so tight. I wonder if any of the penetrating oils will reduce the volume? I suppose if one actually dissolved the rust then it could squeeze out or run out and loosen the joint. As a side note, in Machinery's Handbook, is a description of a method of securing nuts and bolts permanently. It's called a "rust joint". I know this method used to be used for securing fasteners in some bridge construction. One recipe for this method is to pack the joint with a paste made from 80 pounds of cast-iron borings or filings, 1 pound sal-ammoniac, two pounds sulfur flowers, and water. The preceeding recipe is from Machinery's Handbook. I paraphrased it but don't want to plagiarise it. ERS

Yes, it does indeed. I unscrewed an elbow for an Onan exhaust manifold, that was impossible to remove without penetrating oil (PB Blaster). It was impossible to take off, but after liberal spraying with PB Blaster and waiting, it came off relatively easily.

THAT's the nasty stuff I was referring to!

---------------------------- Mr. P.V.'d formerly Droll Troll

P'Blaster is my favorite. Kroil is great too.

Gunner, keeper of rusted shit.

Rule #35 "That which does not kill you, has made a huge tactical error"

Well, we had to replace the front bumper on my old roommate's Bronco one time, the thing came out of Wisconsin so all the nuts were pretty well rusted. We could both do chinups on a breaker bar with a 4' cheater pipe on it, he had about 50 lbs on me. I gave it a shot with some LPS 1 and let it sit. Next evening, after work, we went at it again. Was like removing brand new nuts, the LPS 1 had gone all the way through and had spread out in a 6" circle on the other side.

One of the few failures I've had with the stuff was with rusty exhaust manifold nuts, it's like they weld together with the studs. If the stud doesn't back out of the manifold casting, it'll twist off. You then get the fun of drilling the buggers out and retapping. I use copper or brass nuts on the VW now for exhaust work.

Stan

I am curious though, what is the mechanism why these penetrating oils unfreeze stuck and rusted threads. I understand that they "penetrate" (duh), but so what? Does it dissolve or weaken rust?

Well, oil is slipperier than rust. I suppose it makes the shear line more slippery. A mechanical engineer can probably put that in real terms that may mean the same thing, or I might be wrong.