Total chemistry newbie here (so this may be a fairly obvious question). With that said, I've had a niggling question that I can't quite resolve myself;
Given that galvanic corrosion is driven by the different electronegativities of different elements, why don't alloys made of significantly different elements self-galvanically corrode very quickly?
Essentially, if I were to place two electrically connected lumps in a conducting bath, one of copper and one of tin (with an anodic difference of 0.3V), I would expect them to corrode relatively quickly. Yet if I make these lumps small enough (i.e. make an alloy of them) the resulting bronze mass is fairly resilient. At what size do the individual lumps of copper and tin change from being rapidly corroding to something stable?