batteries don't last forever though. even if you can recharge it, if its corroding, then its going bad. the battery would probably be the cheapest check. if the new battery still corrodes, then check into other things. one of the things you have to narrow down by replacing stuff.. especially with a corroding battery. i've seen a car be affected by a battery spill.. bad times that was..
sometimes, the battery acid is coming from the battery itself. you should hope for that, as i said earlier, its the cheapest fix..