The petro-chemical industries, power plants, and facilities with cooling towers have been dealing with MIC for awhile. As a result, a lot is known about it. The affect does vary between the different alloys with ductile iron corroding slower than steel. There was also a case where MIC caused the water in copper pipe to turn blue. MIC is not caused by a single microbe, but is attributed to many different microbes.
General corrosion affects the entire surface or at least the wetted surface.
MIC, on the other hand, is very localized. It creates a nodule and a pit beneath the nodule. There can be only a few nodules or there can be many. Within these nodules microbes rarely work alone but operate as a mixed community of differing types and groups. The different microbes perform different functions within the community.