There are a few things you can do to prevent the bottom of a cast iron skillet from rusting: Season the skillet regularly. This will create a barrier against moisture and oxygen that can cause rust. Store the skillet in a dry place. This will help to keep moisture away from the skillet and prevent rust. Clean the skillet after each use. This will remove any moisture or food that could cause rust. If the skillet does get wet, dry it immediately. This will prevent moisture from sitting on the surface and causing rust.