Found this by accident but it works amazingly.
We have hard well water at our house up north so we bought some of this from menards for $1.99 to clean the rust in the toilet and it just took it right out which got me wondering if it would work on rusty nuts and bolts, you know the ones commonly found on old tractors.
So I grabbed two red plastic dixi cups one for the bar keepers and one for petroleum naval jelly to do a comparison.
Bar keepers won hands down, after about 30 minutes the hardware it the bar keepers was almost totally rust free and the navel jelly was barely doing anything.
Next came a more serious test:
We have a chevy express eight door van and the rear side doors on both sides had hinges that were so rusted they were beginning to tweak the hinges and I have tried all sorts of penetrants with very limited results.
I mixed some Bar keepers and some marvel mystery oil in an empty 3 in 1 oiler and shook it because those don't actually mix and applied it to the hinges several times as I worked the doors back and forth and it freed up the hinges.
Bar keepers friend toilet bowl cleaner simply eats rust, YES it is caustic so be very mindful of what it touches but it can also be flushed down the toilet after use.Bar Keepers Friend toilet bowl cleaner