When a microwave heats hard water, iron condenses on the interior walls of the oven and forms rust stains. While the rust is probably not harmful, it's alarming to see. Cleaning the rust stains from the inside of your microwave oven takes some patience, but you can make the microwave shine again.
Wipe the inside of the microwave with a damp paper towel or cloth to remove any loose debris.
Mix the white vinegar and cold water in an open microwaveable container and place it inside the microwave. Turn the microwave on to let the solution come to a boil.
Leave the hot vinegar and water mixture in the microwave for two minutes. The steam from the water will loosen any substances stuck to the inside of the microwave.
Remove the hot liquid and wipe the microwave again with a rag or paper towel. Keep wiping until all of the stuck material comes free.
Apply the baking soda and salt to a moist sponge and create a paste. Put the paste on the rust stain and let it sit for 15 minutes. Wipe the paste off and clean the inside of the oven again.
Apply a small amount of bleach to a rag and place it on the stain, if the baking soda paste does not remove it. Use enough bleach to saturate the stained area. Let the rag sit on the stain for 15 minutes.
Wipe the stain with a wet towel. Make a second paste of baking soda and salt and apply it to the area where the bleach was. Let the paste sit for 15 minutes.
Clean the inside of the microwave with a wet rag or paper towel. Wipe every surface thoroughly to remove any residue from the cleaning agents.