Dear Tiquibola*
Thanks for sharing this case
I think you have to inform the rotor material because it is the key thing to identify the damage mechanism
now I know the operating conditions but material of the rotor is important to think about what damage occurred.
From the photos* I can expect that general corrosion which created surface rust layer and i expect that not critical or can cause any problem for the safe running of the equipment however you need to know the reason to avoid subsequent severity.
Please tell us material of that rotor.
Regards