IIRC, this is corrosion between the aluminum and the radar absorbent material. A new problem with construction of stealthy aircraft. Not a simple aluminum corrosion problem.
Yes, your point is correct that when you mix metals or have mixed metals and composites, the stucture becomes like a battery and electrons ‘flow’ between the materials, eating away at one or the other. Boats in salt water handle this by mounting lead fish on the hull. The lead gives up its electrons faster than the steel hull, and the lead fish corrodes, reducing corrosion to the hull itself.
For stealth aircraft to maintain their stealth properties, I do not know if there is an easy solution like with a boat.