Cast iron kettles will last a long time if you take care of them. If you leave the kettle wet too often or allow it to sit in water for too long, it will rust. Rust appears as a brown or red coating on iron caused by oxygen and moisture. Emptying and drying the kettle after each use will help prevent rust, but if it does occur, you can remove it using common household items. If you keep the rust from spreading, it will make cleaning the kettle easier, so if you notice rust on your cast iron kettle, clean it immediately.
Lay the kettle on its side on a flat surface. Place it between two heavy objects to keep it from moving.
Apply 2 to 4 tbsp of coarse sea salt and 2 tbsp of vegetable oil to the interior and exterior surfaces of the tea kettle. Add more salt and oil in this proportion as needed to remove the rust.
Fold a washcloth in half and scrub vigorously. Concentrate the scrubbing on the rusted areas, but cover the entire interior and exterior surfaces of the kettle with the salt and oil mixture. Replace the washcloth when it becomes covered with rust to prevent spreading the rust back onto the kettle.
Use steel wool to remove tough rust stains on the inside and outside of the kettle. Rinse the steel wool frequently while you scrub so that you do not rub the rust around.
Wash the cast iron kettle with dish soap. Rinse the kettle with hot water, and dry it off completely to prevent rust from returning.
Apply a thin coat of vegetable oil to the interior and exterior surfaces of the kettle with a paper towel. Cure the cast iron kettle in the oven at 204 degrees Celsius for one hour. Wipe off the excess oil with a clean paper towel and allow the cast iron kettle to cool completely before you use it.
Do not use dish soap to clean a cast iron kettle after you cure it.