check this thread: http://www.airforums.com/forum...ead.php?t=5264
the problem is not exclusive to the 12v
side of things. I nearly burned down my trailer with the 120v system....same corrosion.
I guess I never updated the thread, but wound up replacing the entire box, as the bus-bar in the photo was also corroded beyond repair. and that part wasn't replaceable....so I had to get a whole new box.
anyway, I guess this is just "what happens" to exposed copper over time. condensation, humidity, etc.