MBdoc - I suppose for him, it’s all relative. Say the burrs do rust on his grinder… he can the. Just go and replace those, for a relatively “low” cost. But for the majority of mortals like the members here… we might be gutted.
For the very little time I used RDT back in the day, I DID see signs of corrosion on the burrs. Coincidence or not, I’ll never know, unless I have a test/control equipment.