Maybe germane -- hopefully -- I was faced with a new challenge day-before-yesterday, as the battery on my DR Field & Brush mower had died. "No problem -- a 20-minute job" to put in its replacement? No way! The negative terminal bolt and nut was rusted/corroded to the "Nth" degree, and I first wire brushed it to get the majority off. I then got some Kroil which -- after several hours -- did not seem to do anything. Similar results with Liquid Wrench. For all solutions, Google, right? I did and recommended was mixing together, at an equal 1:1 ratio, some Automatic Transmission Fluid and Acetone. A quick trip to store got me the ATF -- I bought cheapest they had -- and mixed an ounce or so with an equal amount of Acetone. All I can say is, "WOW!" The mix, dropped on with a glass pipette (I use to make 50:1 into 40:1 by adding 3.5ml per quart), it kind of bubbled a little, and disappeared. I added a few more drops, to get a repeat. With my third application, liquid remained. I put the wrenches back on, and guess what? The nut came off with almost no resistance!!!
Albeit my challenge was with a piece of lawn/garden equipment -- I have experienced similar challenges with firearm disassembly too many times to list... Hence, I thought I'd post this in hopes it may be worth a try for others with rusted/corroded challenges!
geo