Should be able to scrub it off.
Search this forum for sacrificial anode. You can install a little rod (Mg, I think?) in your kettle that'll keep it from rusting. Some people get the rust, some don't. I've also seen posters say they put a dab of olive-oil on it after cleaning and that keeps the rust off. Personally I had rusting the first time I used it, then after that it's been fine. I just make sure it's dry.