Use calcium, lime, and rust remover or distilled vinegar.
Rinse your cast iron kettle clean with warm water. If there are any stubborn rust stains remaining, you can spray them with oven cleaner, wrap the entire kettle in a heavy-duty plastic garbage bag, seal the end off with tape and let sit overnight. Wash the Pour out anything in the pot, rinse it out with clean water and dry the inside thoroughly with a paper towel. Brew a strong pot of green or black tea in a separate pot, bring the tea to a boil and pour it in the teapot. Let it cool for 20 minutes. To clean mineral deposits in tea kettles, you can use calcium, lime, and rust remover or distilled vinegar. Pour distilled vinegar into your kettle and let it percolate through the kettle to remove mineral deposits with help from a professional cleaner in this free video on cleaning kitchen appliances. Best Answer: Try these options seperatly. First. Fill kettle with white household vinegar. Let stand one hour then gently rinse with warm water. If this doesn't work, try CLR-a product you can find in the grocery stores by the cleaning products. Use plastic gloves. Fill and swish around. It may take a few applications.
http://www.ehow.com/how_4914622_clean-rust-cast-iron-kettle.html http://www.ehow.com/how_7897866_clean-rust-teapots.html http://www.youtube.com/watch?v=RNHSoZ16qzY https://answers.yahoo.com/question/index?qid=20070813184534AAm6VXK
how do you get rust out of a tea kettle