I've used straight vinegar once or twice and worked well on small parts and a chain. Might try a pinch of salt next time.

There was a mention of muriatic acid(pool acid) in that thread...tried it once, but must be diluted significantly, too strong. Worked fast, an old french freewheel looked new, while a chain had its plates become loose on the pins. It does attack chrome, the plating flaked off.