easy, cheap and ......
to derust and cure and iron pan.
wash and scrub with abrasive pad or use a tool like a dremmel tool. but just a brillo, steel pad and some elbow grease until most of the rust is off, should be more than enough.
the dremmel would be for deep rust that comes from nonuse.
wash until water is clear.
then put cooking oil in the pan and set on stove under a high flame until the oil is hot.
then turn fire off and leave pan and oil cool.
when oil is cool use towel to wipe around the base of the pan, repeat this til the pan is clean and smooth enough to fry lard or bacon in it... do not fry til stick or burn fast. this is the first trial run to get the pan back in shape.
this is also the speedy and cheaters way to cure a pan.
stir bacon often...
cook til bacon is the way you prefer and remove from pan, use spatula (hard) to scrape any bacon material from the surface if it has stuck. but what you should have is now a dark, glossy surface to the base of the pan.
wash briskly with dish detergent and a soft scrubbing sponge.
(don't toss into the dish washer if you have one) do not scrub entirely clean just scrub til the pan is clean of the residue and oils from the bacon grease.. wash with hot water.
stick back on stove and turn fire up.. let pan dry to the point the moisture has just evaporated.. then put a coating of cooking oil on the base and rub into it with a towel.
let set.
keep this up and keep from burning things into the pan and washing it by hand gently.. soon your pan is cured and should be relatively nonstick, of course using a oil base or grease to coat it before using it.
there are many ways to do this, this is just one.
this is rather fussy but if you keep it up and don't burn anything in the pan... sooner or later you'll get a deep black pan with an almost mirror gloss.
this takes a bit of time and effort.. but this will keep the pan protected and you shouldn't have to go through this too often.
also whenever you get a bit of rust just mild scrubbing using a scrubbing sponge, then use the oil and bacon technique to fix it back up.... (you can eat the bacon now)