[EricH]

I asked my dad (who used to work with composites for a living). His first comment did not have to do with welding, but with a galvanic issue. Apparently, aluminum and graphite don't like each other, and the effect is accentuated by moist environments (which would probably include at least part of Missouri). It's a slow process, but you may want to add something between the two and hope it hasn't started.

His second comment was that the heat will transfer. If you can remove the box from the aluminum, that's your best bet. Otherwise, use some way of getting the heat off of the aluminum if you can.