Is naval jelly hard on metals?

My sisters thought that it would be funny to bury my bike chain in the back yard as I was putting it back together. I found it yesterday, all rusted and caked in mud. Since I have no money, I decided to bust it out and clean the chain. I washed it first, then banged it out on my basement floor to get the stubborn crud out of the rollers, then I put it in naval jelly for about a half hour to get the rust off and get a nice shine. After I rode it around the block full speed, I lean a touch forward, and the chain basically disintegrates. It was in pieces, as the vast majority of the links had cracked. After I had banged it out and put Naval jelly on it, it showed no signs of wear, and looked brand new. What the heck could have caused it to shatter like that? The naval jelly? Or me banging it out on the floor? I have another chain, which is a touch rusty, and I would like to know if Naval Jelly is safe to use on it, without having it shatter.