Can you send a picture? What's the part number of the chip? Chips have a metal lead frame inside the plastic that leads in closer to the silicon die, and then the die is bonded to the lead frame via tiny copper or gold wires (probably copper in this case). Even if a pin corrodes completely off the chip, you may be able to carefully scrape the plastic away from above where that pin enters into the plastic chip package and solder a wire from the lead frame to the board. If it's a commonly available chip that doesn't require any programming then swapping it will be just fine.