I have Rust
copied from here~
1. If rust is not too bad, scrub with a scouring pad and rinse well. Put over a heat source to dry out all the moisture. Lightly re-season.
2.
The way the pioneers did it was to place the pot in a larger container and stuff with hay. Dry or moist makes no difference. Add enough water to cover and 1 to 2 cups of
cider vinegar. Just let is sit for about 1 hour, then check to see if all the rust is gone. If not, scrub a little and let it sit for 1 more hour; and all the rust should be gone. Scrub with a scouring pad, rinse, and re-season the pot. Remember to use the proper tools and hot pads to do the seasoning since the pans hold their heat . Never touch a hot Dutch Oven without good hot pads. This also works on tools!!!
3. If your Dutch Oven is extremely rusty, this could take 12 to 24 hours of sitting in the solution before you are down to the raw iron.