As a result of regular water boiling, rust can appear in the electric kettle over time. Cleaning this rust can be challenging, especially keeping in mind that you don't want using strong chemicals in a kitchen appliance that directly contacts with water you drink.
Fortunately, there are some methods to remove rust effectively and without any risk for your health. Interesting, that you can even use... Coca-Cola. :)
Our favourite methods of removing rust are thoroughly described here and here.