Multistrada V4S paint issue

Hi everyone, this is my first time on here. Im not sure if anyone has had this problem, the generator cover on my bike is painted a darkish blue with a fine hammered finish. I brought it back in some really horrible weather after a service, which covered it in salt from the road. After cleaning it I noticed that the cover was stained. Ive tried everything I can think of to remove it but it won’t shift. does anyone have any ideas, what might have caused it and how I might get it back to its original state. Thank you in advance.

I’ve not seen that, not on a V4 s, how old is it ??

Its a multistrada 2021 V4S sport