2001 Jeep Cherokee Front Brake Rotors

First of all - He said the iron oxide dust doesn't cause corrosion so the the question of its rust inhibiting properties is moot. Apparently the theory of why rotors get stuck on hubs is that no oxidation is involved, instead a glue is formed when the dust from semi-metallic brake pads mixes with water.

As for ir "Without doubt, it is the most important barrier pigment used in coatings to protect structural steelwork from corrosion. It has a 100 year record of successful use on many types of steel structures throughout the world."

And if you read farther it says iron oxide pigments have protected the Eiffel Tower for more than a hundred years.

-jim

And you're calling someone else a "high school level idiot"? Au contraire mon frere, kindly take a gander in the mirror.

The discussion was about the natural occurrence of rust in ambient conditions.

Unlike such fools as yourself, I don't pay unnecesary extra fees to third parties for usenet access.

Black oxides, MIOs etc comprise, but do not solely consist of, iron oxides.

And if you could start to understand what you read you might one day be dangerous. No amount of smoke screens or the usage of slight of hand will allow anyone to successfully confuse the issue that naturally occurring rust provides any effective form of corrosion resistance, the truth is in fact quite the opposite:

Wikipedia is the high school pimply faced guru' s refuge, eh?

Why, because you know a lot about paint?

This was actually called dissolved oxygen when I was testing boiler water in the Navy. But it was clear what you were speaking of to anyone who has tested water or knows about boiler tube corrosion.

--Vic

This make sense to me. I don't see pad material making rotors stick. But I'm not going to discount what aarcuda says either. In a week or two I'm going to put new rotors on my '97 Lumina. Pretty sure they're the originals. It's only had semi-metallic pads. I'll take a good look at the hubs and rotors and report what I see.

--Vic

Why? Jim is applying conditions used in industrial process where an expected product or outcome is desired (ie., paint, make-up, polishing compounds), I'm talking about a reaction with unknown quantities of radicals such as sodium chloride and magnesium chloride. His version so far has been limited to what happens with one version of iron oxide/oxidized iron. I'm no chemist but I'm pretty sure there is more than one version of iron oxide.

That would largely depend on where you live and what climatic conditions your vehicle is operated in.

I have a 39 year old Plymouth with the original brake rotors, they have been operated in winter on salted roads, the brake pads are 100% organic, not metallic, there is NO rust bloom on the rotors even after

39 years like what I see on 2-3 year old brake components that have metallic brake pads/shoes installed. Anecdotal? Certainly.

Have you ever struggled to remove a brake drum because there was a rust lip formed on the inside edge of the drum? Is that rust lip the same as the surface rust on the outside of the brake drum? One can be easily knocked off with hammer taps much like removing welding slag, the other, not so easily. One occurs because it was deposited there, the other because of elemental oxidation.

The perfect test bed. I wouldn't mind hearing from Jim regarding how many brake jobs he's ever done on this exact chassis.

Take a good look at the threads on the end of the bolts that fasten the caliper bracket to the steering knuckle, compare them to another similar bolt located farther away from the brake assembly. If you're anywhere in the rust belt, you'll find that your T-60 Torx bit will not want to engage quite so easily, you may have to dig some crap out or tap it in with a hammer. The bell shaped spacer, does it spin freely or is it stuck? That's a plated bolt/spacer assembly, not quick to rust/seize on its own... And if you don't break at least one T-60 bit removing those caliper brackets from the knuckle, your operating environment does not qualify sufficiently to make a determination of whether what I'm saying is true.

Sure, dissolved oxygen is the common term.

Unbound oxygen, at any rate, was the point.

At high temperatures, you dont even seem to need dissolved oxygen to get a thin layer of magnetite, but it can be very difficult to measure dissolved oxygen as you approach 0.0 concentration. Rogaland Research in Norway tried to do these determinations between 0.0 and 1.0 ppm as part of a doctoral thesis, but I think they ran afoul of analytical error in trying to determine the corrosion rate versus dissolved oxygen concentration at very low values.

At any rate, enough of brake rotors.

Passivation (if that is what you are talking about) is a function of PH. The way I understand it in a boiler if the water is alkaline the iron can form a rust resistant layer of iron oxides. That is fairly stable and offers good protection as long as the water remains alkaline. The rust inhibiting iron oxides will fail if the water becomes to acidic.

Every word of the above is BS.

Your the one claiming that brake dust is what caused the OP's problem. I'm the one claiming that we don't even know what is in his brake dust. As far as I know the OP has never said what kind of pads he has. You insist he has cheap semi-metallic brake pads and that caused his problem. I say he could just as easily have that problem if he had ceramic pads.

You might also consider, rotor composition isn't the same for all rotors.

First of all brake drums use a different type of iron and the drum brake pad material is different also. And usually the lip exists because the material has not been worn away like the rest.

If it has been 12 years and driven in salty winters it will be rusted. That would happen even if ceramic pads are installed.

How can anyone determine if what you say is true? You haven't said anything coherent yet.

Are you claiming the iron oxide from the brake pads causes the rotors and other brake parts to corrode?

Or are you claiming all the rust you see is all brake dust rust and underneath that rust is a completely untarnished brake components?

And what exactly does the rust on the torx head bolts have to do with the rotors being stuck?

I never denied that iron from pads doesn't contribute to the accumulated layers of external rust on brake components. You haven't explained how you think that rust accumulation has anything to do with the rotors not breaking free from the hubs. If you put a thin coating of anti-sieze or water proof marine grease on the mating surfaces of the hub and rotor they will come apart easily even if the rust accumulation on the outside is worse than what you describe. I have seen rotors rusted so bad that they collapse because the internal ribs have completely rusted away.

And if you break a torx bit it is because the threads on the bracket and bolt have become rusted. That is not caused by brake dust it is caused by the metal on the threads rusting. Sure once you get it apart the threads may clean up and look like new. That is because the clearance of the threads is so tiny that all it takes is a very tiny tiny surface layer of rust to form on the threads and that tiny bit of rusted metal from the threads expands and takes up all the remaining clearance space. Again if you put a good coating of marine grease on the threads before assembly you won't have any problem with disassembly.

-jim

Foundational concepts such as reproducible results and the providing of evidence in support for one's claims are unfortunately but understandably far beyond the scope of charlatans (ie, you).

Albeit now a quite old story (though no doubt news to those of your tragically sorry ilk) the prominent scientific journal Nature long ago researched, assessed and documented the fact that "Wikipedia is about as good a source of accurate information as (is) the Encyclopedia Britannica", you cravenly truncating, goofball phony. I'd be intrigued to discover just who it might possibly be that you think (or perhaps more likely accurate, so desperately hope) that you're kidding.

Passivation can include a number of things. pH in boilers is normally held somewhat above neutral to deal with acid gases, etc. But passivation can encompass a lot of other factors. pH is not the only factor, but is an important one.

Stainless steel would not be corrosion resistant if it were not for the formation of passivating layers of chromium oxide on the surface of the alloy. In general, NO alloy is more corrosion resistant than the pure metal from which it was derived. (Nota Bene...in general)

If you have a nice film of magnetite, even carbon dioxide (or carbonic acid) does not attack very quickly.

Now, at high temperatures carbon dioxide is not held strongly in solution but rather is degassed into the overhead. This is why I said that corrosion normally increases with temperature as do most chemical reactions. In this case, it is not necessarily true.

If you had a strong acid like HCl, or others, then all bets are off. These strong acids are not normally discharged in the vapor, and may attack strongly. Chlorides can be a bitch when you have granular castings with the possibility of intergranular attack.

Even the salts of strong acids can be very corrosive.

In the braking situation, water and electrolyte concentration (often road salt, NaCl, etc) is powerfully involved. Oxygen concentration at the surface of the rotor can be assumed to approach the value of oxygen in the atmosphere.

Temperature cannot be avoided.

Bottom line...if you get your brakes wet, and let them set up and dry, you can have some pretty severe oxygen corrosion.

Eat prick and die, shitteaux

And an unmitigated, sexually obsessed (re: "Hey, c*ntface...." & "Eat prick and die, shitteaux") goofball at that. Do you actually kiss (or whatever other despicable acts you cretins almost assuredly perform on or subject one another to) your ill-fated, deviant mutant progeny and mate with your orifice?

OP Here.

I do not know what pads are currently on this vehicle, or what may have been on it in the past. The vehicle belongs to a friend of mine, and he actually just recently purchased it from a third party.

I was simply trying to help him get the rotors replaced. BTW: we have not yet had time to return to the project, so I still don't know what it will take to remove the rotors.

Cut laterally (along a dimaeter line) into the rotor with a sawzall in three places and hit the pieces with a big hammer.

Ed

Tegger wrote in news:Xns9C5E4C7AB552Etegger@208.90.168.18:

Sorry, typo. It should have been: The rust-choked ROTOR had to be scraped over the hub...

The job is now complete. It took the BFH, applied enthusiastically for ten swings or so to break the rotors free.

We then learned that there are two different sizes of rotors for a 2001 Cherokee. with the difference being 6 mm of depth from the mounting surface to the outboard braking surface. Why do I always need to learn these things the hard way?

If your Jeep has the shorter ones, and you install the longer ( taller? ) ones, the front wheels cannot turn once the lugnuts are torqued down.