It's normal happens from wear but you should be covering your food with cling film this stops a lot of the steam & condensation thus not adding/causing any more rust also good to cover your food anyway as how often does one clean the microwave? Every day, every week, every month?
The only way to truly avoid this is to buy a microwave that has stainless steel inside which is much more hygenic.
mine, about 5 years old, has a little rust on the edge where the door closes over. It doesn't seem to affect anything, doesn't touch the food so I'm not worried. If it were eating away at the workings of the oven, I might be more worried!
mine, about 5 years old, has a little rust on the edge where the door closes over. It doesn't seem to affect anything, doesn't touch the food so I'm not worried. If it were eating away at the workings of the oven, I might be more worried!