flanso 

Stuart, I saw a thread on BITOG, an automotive forum, where a poster is extolling the virtue of cleaning aluminum in a crock pot, at low temperature overnight, with the parts submerged in aluminum compatible automotive antifreeze. The parts "come out looking like new," he says. There is even a current thread on here about using a crock pot for cleaning but without mention of the antifreeze. I would appreciate your opinions on this antifreeze thing. I make the assumption that the guy does not return the crock pot to pot roast duty.

cyccommute 

I can’t see how it would make a difference. If the point is to remove grease, there are better ways to do that. Ethylene glycol (antifreeze) doesn’t do anything to aluminum so it shouldn’t clean it or brighten it or anything. The heat might help but the engine is far hotter than a crock pot. Propylene glycol (RV antifreeze but it works in cars) is slightly less compatible with aluminum but only slightly.

Side note: We should use propylene glycol in our cars. Ethylene glycol is metabolized to oxalic acid which precipitates the kidneys and causes renal failure. Propylene glycol metabolizes to pyruvic acid which is made during the Kreb’s cycle anyway. We basically can eat the stuff and live off it. (Not that I would recommend that)

dsbrantjr

Ethylene glycol has a sweet taste to which dogs and cats are strongly attracted, and it is very toxic to them. So store it safely and keep contaminated drain pans and the like away from animals' access. I believe it has also been used to deliberately poison people.

Gresp15C

Indeed, PG used to be in some kinds of salad dressing.

HillRider

Antifreeze is more than just ethylene glycol. It contains corrosion and deposit inhibitors and perhaps those did clean and brighten the aluminum as the poster was claiming.

BTW, the current thread here asking about a "crockpot" turns out to be a typo. The OP was really asking about an ultrasonic cleaner.

cyccommute 

Corrosion inhibitors would prevent the removal of metal. I really doubt that any of the inhibitors would have an effect on the oxide layer on aluminum as well. Aluminum readily oxidizes when the oxide layer is removed for any reason. If the oxide layer were removed to expose the metal, the metal would oxidize rapidly (it’s nearly instantaneous). The new oxide layer would be removed exposing metal which would oxidized, ad infinitum. Eventually the part would dissolve.

As I pointed out above, a crock pot doesn’t reach the temperatures seen in an engine. Aluminum parts in an engine would undergo the above much more rapidly and the removal of metal would be accelerated even further.

You have more information than the rest of us seem to have. The action of anything in the antifreeze would be even slower in an ultrasonic cleaner since it runs at an even lower temperature. If the parts are in a ultrasonic cleaner, it may be that the antifreeze does nothing and the ultrasonic cleaner is doing the cleaning. People like coming up with elaborate cleaning schemes all the time. Correlation doesn’t necessarily imply causation.

HillRider

Yes, thank you. I know the chemistry of aluminum oxide layer formation. I was just wondering if the additives in antifreeze could have explained the cleaning effect (if it really happened) the OP mentioned.

The only information I have was from reading the thread where the OP clearly says he was asking about an ultrasonic cleaner and the crockpot mention was in error. That thread had nothing to do with antifreeze at all.

Mista Sparkle

Aluminum is rather reactive, so you do have to be careful what you try to clean it with. Some things easily dissolve is, others build an oxide layer rather rapidly.

I would avoid putting aluminum in an ultrasonic cleaner as the cavitation will start pitting the surface rather rapidly. Depending on the shape of the object and the desired finish there are several options for cleaning aluminum. If the part is anodized, you want to be careful about not using an aggressive cleaning technique as the anodization reduces the likelihood of corrosion on the parts. White scotch-brite and an appropriate solvent for dirt and debris. For bad spots, only mild abrasives should be used.

If the aluminum is not anodized (don't forget a lot of aluminum parts are clear anodized) and just bare, I have found mothers mag and aluminum polish to be amazing. Not that it has any relevance here, but I have polished aluminum with the mothers aluminum polish to the limits of somebody's fancy emissivity tester, somewhere ~0.02 for a cryogenic application. Shiny polished aluminum will likely require maintenance but if pitting is not allowed to occur, it is not too bad.

cyccommute 

Other people may not know the chemistry of aluminum oxide.

The additives that I see in the automotive antifreeze are sodium salts of fatty acids. Those should have little to no effect on the aluminum nor the oxide layer.

Which “OP”? flanso is the OP here and he hasn’t said anything other than his original post.

TobFromme

I think this is thread being referred to:

https://www.bikeforums.net/bicycle-m...-crockpot.html

I'm still confused about the statements though, as the OP there didn't mention ultrasonic at all. :confused:

cyccommute 

That's not flanso's thread nor has he posted there. His question comes from BITOG which he says is an automotive forum.

TobFromme

flanso mentioned another thread about cleaning with a crock pot and I think HillRider is referring to that thread. At least, that’s what I think is happening.

flanso 

Here is the actual post that I found on BITOG, www dot bobistheoilguy dot com/forums/ubbthreads.php/topics/5460940/1
It is the post on which I asked Cyccommute's to voice his expert opinion:
"Is this true or no?
Something we radio control airplane guys use to clean our glow engines, is an old Crock-Pot that has the ceramic removable tub. Fill it with antifreeze that is compatible with aluminum, disassemble the carb and put it in the crockpot on low overnight.
You can drop an entire glow engine into this solution, and it will come out looking brand new. The ethylene glycol dissolves the varnish deposits that the burnt methanol, nitromethane and castor oil fuel leaves on the engine, and doesn't harm the metal at all. Most glow engines are aluminum castings with either brass plain bearings or steel ball bearings, it doesn't hurt any of the metals."

TobFromme

I can't see how it would hurt it at all. Any testers?

cyccommute 

Different animal than what I thought originally. I was under the impression that the cleaning was on automotive parts and that metal from the part was removed.

In this situation, the engine is a 2 stroke where the oil is added to the fuel for lubrication. Because of it’s molecular structure, castor oil is more polar than other oils so It may be more soluble in a polar solution like antifreeze and water. Water alone is more polar but that addition of the antifreeze would decrease the polarity. Perhaps there is a sweet spot where the polarities match and the oil dissolves well. Heat would help.

Castor oil is also more easily derivatized then over vegetable based oils due to its structure. It may react with the nitro group in the nitromethane during combustion and make a polymer that is more water soluble than others. Again, there may be that sweet spot where heat, polarity and molecular structure come together.

I would have thought that given the toxicity of plant from which castor oil is obtained, it would have been phased out long ago but, apparently it has some unique and useful properties,

Bottom line: While the antifreeze won’t have any effect on the metal and it probably would be useless on lubricants used for bicycles and automobiles, in this case, it might just work to remove the fuel varnish for the rather inefficient 2 stroke glow engines.

One caveat: The above contains a lot of hand waving. I’m certain that antifreeze in a crock pot wouldn’t clean bicycle parts. Cleaning of glow engine parts is (almost) pure speculation. I haven’t tested it nor could I say that it is the best way to do the job. Carburetor cleaner is a mixture of methanol, toluene and acetone in equal amounts. It’s fairly polar which would be in line with the water/ethylene glycol.

flanso 

Stuart, Thank you, I always appreciate your posts.
Frank