Evapo-Rust.
I saw this thread and thought that I would add that I found the Evapo-Rust product in a saturated wipe form at
www.ALLINTERNETSALES.COM . They sell these in 20 and 100 counts canisters and using the 20 count, I had success in removing flash rust from my bumper and some heavier rust from a door track.
Mick