Scrub the rusted area with steel wool or a stiff brush
Wash with warm water and mild dish soap
Rinse thoroughly and dry completely
Apply a thin layer of vegetable oil or flaxseed oil
Bake upside down in the oven at 450–500°F for 1 hour
Let the pan cool in the oven
Repeat seasoning if needed
Store in a dry place
Avoid soaking cast iron in water
Re-season regularly after cleaning