We've discussed several ways to season cast iron here at Lifehacker, but what if your roomie let your cast iron soak in water overnight, or heaven forbid, put it in the dishwasher? Grab an abrasive pad and some white vinegar. With a little work, your cast iron will be as good as new.
Instructables user theabion points out that all you need is some white vinegar, some water and an abrasive scrubber to make your rusted, damaged cast iron gleam like new. Mix the water and vinegar 50/50, and let the pan soak in the mixture for an hour or up to six depending on how bad the rust is. Then gently scrub the rust away from the cast iron pan with your scrubber. He used a copper pad, but you could also go with our trusty salt scrub method to remove the rust and debris as well. Whatever you do, make sure you're complete and remove as much of the rust as possible.
Once the core of the pan is clean and the rust is all gone, it's time to re-season your pan. Theabion suggests a good rubdown with lard and a bake in a 135C oven for 15 minutes to let the lard drip off, and then crank up the heat to the smoking point of the fat and bake for another 45 minutes. At this point though, you can season however you choose -- the key is using the vinegar and abrasive scrubbing pad to clean off the rust and save your cast iron. Have you ever had to rescue a good cast iron pan? How did you go about it? Share your tips in the comments below.
Rescuing Cast Iron [Instructables]