I used Oxalic acid to remove the rust from my Miyata 1000 frame.

I got it at Lowes and it's labeled as deck wash. From what I've read, you should dilute it by 1/4 what they want you to do to wash your deck. I wasn't that precise. I just poured the entire gallon jug into the bath and filled it up with warm water. Worked perfectly and only took a day to dissolve the rust.

I just lined a bike box with plastic and filled it up.