Of the ones I've tried, I've found "Magica" ( www.magicarustremover.com
) to be the strongest and easier. I'm pretty sure it's oxalic acid. Get
the little tube which is a gel. This is particularly easy to dab onto
stainless fittings and screw heads without getting the stuff
everywhere. Wear rubber gloves anyway. (I have no relation to the
company).

Practical Sailor also just ran a test and like Star Brites rust remover
a lot which is also oxalic acid.

Carl

FSR is a blue gel that has oxalic in it. Stays put while it works and
can be found at most marine stores. I'll let you figure out what the
initials stand for.