I’ve had good luck taking chains apart in a big clear plastic bag. Can’t lose the link like that. I’ve been able to free up most chains by soaking overnight in Evaporust (if rusty), washing with dishwashing liquid and an old toothbrush, drying and soaking in a jar of kerosene for a year. It helps if you shake the jar at least quarterly. Don’t use vinegar to take the rust off. It doesn’t work very well if you give it a short soak and if you forget and leave it more than overnight, you’ll probably only find loose links in the bottom of the tub. Don’t ask me how I know this.