All,
A bit late to the party here.... but some rust disolving solutions now available....
WD-40 is not a rust dissolver. It is a Water Displacement from the 40th mission of one of our space adventures back in the last century! Used to keep ice off of the space craft.
That said, some dis-solvents that I like:
1) PB blaster. It works, but it may take some time........keep soaking what ever you are working on and testing it with a wrench etc...... I've had it work quickly and on other bits, perhaps a matter of weeks......(non-crucial project....)
2) Evap-O-Rust Non toxic solution dissolves rust. Not sure about it's penetrating qualities..... Soaking for 24 hours usually cleans small stuff up. I have used it to remove surface rust from small steel bits, nuts and bolts, bezels, brackets, before painting. Doesn't seem to harm zinc or chrome coatings. Will sometimes leave a blackish coating that you can wipe off or remove using a soft brass brush so as not to dork up the metal surface finish. I find it much easier than chasing parts around the garage after the wire wheel flings them into the dark abyss....!
It does absorb moisture from the air, so use it in a closed container if possible......I keep a small collection of plastic "Costco" type containers from snack foods etc to do various size pieces. Tougher with a set of lower arms, but me fears that I will need to do the same operation soon! It's bugging me not knowing......
Once done with it, dump it into the toilet (probably not for septic systems!) or give your lawn some more iron..... won't hurt it.