The BB area has the patterns of galvanic corrosion. https://fastenerengineering.com/...orrosion-prevention/ . Moderne frames are constructed with layers of fiberglass at bonding interfaces to prevent galvanic corrosion but I don’t know when this practice started. Certainly the original carbon frames where carbon tubes were bonded in alloy lugs suffered from significant corrosion issues.

very nice, and I have no reason to doubt your assessment. It makes sense, now that I have looked it up and done some web searching. Thank you, very much.

The Aluminum cable guides appear to be suffering from the exact same thing.

so, how do we feel about this, especially on the BB? alarmed? or is it just an inconvenience on a bike that is going to see light duty for the rest of its life?