I been learning.
I know this thread is old,but I have been down and out health wise.I been piddling along at times and hope that I have a little here that may be of help to someone as it has worked for me.
I have been using a "Chicago Electric power Tool" 1-1/2 quart Ultrasonic Cleaner Model 91957,tank size 4"D.x9"L.x5 1/4"W for well over a year now.It was purchased from Harbor Freight.I have been very satisfied.
Things that I have learned that have worked for me.It will EVENTUALLY free up to Great working order WITHOUT disassembly rusted and frozen up things such as a German double set trigger,frozen up since 1986 and a US.Gov.padlock buried in the sand on a Barrier Island since WW2 and dug up in 1990.Each of these now work great,and I do believe that they both would have been totally destroyed had they been forced in any way.The solvent used in the cleaner was Distilled Water!Rusting was not a problem as the ultrasonic cleaning removes the gases out of the water,so no rusting could take place over the days cleaning.The objects were left in dirty water in the containers with a lid tightly screwed on to prevent the water from absorbing oxygen to prevent rust.Clean water was used at the start of each new cleaning cession.
After a final rinse,a run in Distilled Water and cheap water soluble "Cutting & Grinding Oil" bought by the quart as part Item#: SL2512 or by the gallon part Item# SL2513 from your NAPA Auto Parts store.A very little goes a long way when mixed with water and I have seen no sign of rust after 4 months in our humid South Georgia climate.This is a whole lot cheaper and so far has worked every bit as well as the high priced stuff that I was given to try.
I use "Ball" Wide Mouth canning Jars in 1/2 pints,pints,quarts and 1/2 gallon sizes that fit inside my cleaner,with the water kept up to the correct level inside the Ultrasonic Cleaner.I can use whatever level of water that I wish in my jars,with the level being way higher than the level in the cleaner.The high water level in the jars will eat Aluminum Foil,so I am getting ultrasonic cleaning action.
My jars set on the "rack"that came with the cleaner.The cleaner will take two of all sizes of jars at the time.I use strips of inner tube from any tires tied around the Jars to keep them apart and off the sides of the cleaner.I bought my 1/2 pint,pint and my quart jars at the grocery stores in the canning supply section.I got the 1/2 gallons at a yard sale.You could still buy the 1/2 gallon online last summer.
I sometimes use pieces of plastic "drawer liner" cut to fit,to cushion my jars when ever I cannot suspend the parts by wire from the top of the jar.I use the drawer liner that looks like the "Expanded Metal"with the Diamond openings.I do believe that this absorbs some of your sound waves and slows your process.I found that a simple "rack" that you can use to support and suspend small caliber actions still attached to the barrel works well with this cleaner and jars.
I use no flammable fluids as as my instructions say not to.
I free up and clean Aluminum with Mobil 1 Synthetic ATF.I have worked in maintaining,Firearms,Logging,Agriculture equipment,US Submarines,Fresh & saltwater Marine equipment,including engines on commercial & small boats,sport & commercial fishing equipment,pulp and paper mills and 3 chemical plants for 50+ years now and it is the best thing that I have found so far.It even works for bathroom and farm situations where you have urine,manure and fertilizer corrosion.A drop in a joint a day will eventually work if anything will.Wipe it down and rub it in ,it gives the Aluminum a polished look while it protects!As others on here have said about ATF,It is a great penetrating oil.Now,I do not know about other ATF fluids as I have not tried them.
One other old time tip.I use to love to watch and help a old gunsmith in the early to mid 50's on the North Shore of the Santee.He used a old fashioned pressure cooker to boil crudded up and frozen up parts in!He would repeadedly pressure it up and cool it down.Cooling it down completely over night.Sometimes it took days,but it works.Expansion and contraction?ALFRED