Try a vinegar and water solution. Forget about how much of each you should use, just pour at least one teaspoon of vinegar in a glass, fill it with water and carefully pour the mixture into your frying pan. Bring it to boil which may help break down the residue. After that, remove as much rust as possible while scrubbing the affected area with coarse salt (or baking soda) and warm water.
Thousands of people are using cleaning methods similar to this every single day without any problems but first be sure to read the disclaimer below.
DISCLAIMER: Please note that if you decide to give this method a try, you do so at your own risk . I accept no responsibility for damage caused by applying my suggestion how how how how how how how how how how how how how how to clean bottom of pans.
How to clean bottom of pans
Remove all food from the pan and rinse it with hot water
Add 1/4 cup of baking soda to the pan, let it sit for 5 minutes
Add a couple drops of dish soap and scrub away any leftover food particles
Rinse with hot water again to remove all traces of baking soda or dish soap
Dry thoroughly before use – do not wipe down with a towel as this will scratch your pans!