There are special descalers on the market, but white vinegar works just as good !

There is a product called CLR which may work, but I’m not sure if it’s suitable for kettles.

Lemon!
Slice up a lemon, pop it in, boil, rinse, repeat until all stains are gone.

I did notice a new kettle cleaner in Big W but I’m not inclined to try it because of the chemicals.

I use a slice of lemon. Pop it in the kettle and boil, repeat as necessary. Maybe add a little bicarb of soda with the slice of lemon for stubborn stains. Rust may never come off though, so be warned

Soak it in vinegar for half an hour and rinse well.

i use a whole lemon just slice up and put it in the kettle skin and all and boil acfew times then tip it out and rinse kettle i was shocked at the results when i tried this and its all natural and cheap,bottlevlemon juice works too

I use CLR buy it at Coles swish it around the Kettle and there you have it all clean. Rinse with white vinegar and then boil twice to clean with no taste or smell.

Following- great question

Boil vinegar and bi carb soda and the rust will just bubble off

I couldn’t clean the rust from my kettle and was advised by a little old lady to put a large marble in the kettle. So in my new kettle this is exactly what I did and have to say it is successful, no rust.

Buy CLR. Calcium Lime Rust Remover. CLR is the most powerful cleaner for dissolving tough calcium and lime deposits and surface rust stains from a variety of surfaces. I use it to clean the shower heads and toilet so many other uses as well.

I use citric acid for scale in our kettle ,1teaspoon in kettle boil ,let sit till cooler ,tip out & prince fresh water .

Bicarbonate soda. Let it sit in the bottom for a few hours. Then pour a little vinegar. Sit again and rinse out. Lemon is also a great option to boil in the water to clean out.

A descaler works wonders but for a natural option I add lemon juice & obviously boil water!

How amazing is vinegar? ….we use it for everything