I got to spend a couple of recent evenings working on the men's Schwinn New World bicycle. The basic bottom bracket components are all cleaned up (previous entry), so now it's time to start working on that heavily caked and frozen chain. I did not see rust on the chain, just a ton of caked and dirty grease gunk.
I looked through my shelves and found some nice stuff for the job. I find the best way of attacking a chain is to soak it. If the chain is very rusty, I might degrease and soak in Oxalic Acid. However, if the chain is not rusty, then sometimes an industrial strength de-greasing/de-gunking is needed.
Here is what I mustered:
-Kroil and/or Liquid Wrench to preliminarily loosen the chain and soften the gunk
-A paper or plastic bowl (I used 3 paper bowls kept together as a stack for this)
-Plenty of clean gear oil
First, I sprayed some Kroil and Liquid Wrench into the chain's joints to loosen it up. I want to be able to fit the chain into the bowl, which means lots of bending. The chain was initially pretty frozen up, so the very these very thin penetrating oils help to loosen it up for that.
Second, I place the chain the bowl of gear oil for 2-3 days. What I'm using is 80W-90 gear oil from a local autoparts store. This particular oil is very good at wicking out the gunk from the small spaces of the chain. The oil is meant to keep car gear surfaces clean and lubricated. In this case though, we want a cleaned and lubricated chain. The soak length helps to break down the grease and wick it out from the small spots. You could feasibly soak it longer, but by the end of 2 days, my oil was pretty dity. The gear oil goes into the bowl an nice amber color, and comes out looking like... well... used oil. There really as a lot of junk on this chain.
Remember to wear gloves when dealing with this oil. This gear oil STINKS. It smells like very, very intense body odor. If you get it on you, you will smell like the body odor. If you go into public, people will think you have body odor. They won't buy the gear oil explanation, unless they happen to be car mechanics.
An example of the used oil is below- remember this stuff was that nice clean amber color that oil often is, when it came out of the bottle. All that darkness is crap from the chain.
Third, after soaking begin to rub the chain down with the rag. Work the chain along in your hands, moving each link on the rag and giving them a little flex to loosen them up. If the rag becomes cruddy, get another rag. It may take several. You should eventually begin to feel the chain loosening up and the gunk should be disappearing. If you have too much gunk, repeat the process until the chain is ready.
When you are finally done, wipe the chain down with a clean rag and remove as much excess oil as you can. This oil will attract dirt, so you want to have as clean a chain as possible. Finally, once your gears are cleaned too, hook up the chain and spin the mechanism. Do this outside and don't spray yourself. The oil will be flung off like a wet dog shaking off water. Run the rag along the chain again as you spin the mechanism. Once satisfied, your chain should be much cleaner and more pliable.
As you can see below, it looks improved, though I still have to clean up the rear cog and the wheels.