Soak them in a vinegar and salt bath ... that surface rust (or any rust) will come right off with a light scubbing from an M16 brush after soaking in a vinegar/salt mixture for a few hours. No damage will happen to the mags either. I'd just take them apart and soak everything. Check youtube for details on this method if you don't believe.
Soak longer for heavier / deeper rust
I've done everything from gun parts, to expensive garden tools left outside by accident, to complete restoration of a very old wood stove .. works great!!!
Coca-Cola does not work btw (at least not nearly as well), as some would have you believe. lol
ETA: once you are happy with the rust removed, be sure to rinse well ... then oil & wipe excess off springs, mag bodies etc and reassemble. They'll look great
Good luck to ya!!