After having a new aluminum battery box made, you might have a spray-in
pickup bed liner shop coat the insides of your new battery box. You can
also get this stuff in spray cans and do-it-yourself. It's very much like
plastic tool handle coating. It needs to be thick so it doesn't get any
holes in it where acid can get under the coating and corrode the box.
How about just putting a layer of bicarbonate of soda in a plastic tray
for the battery to sit in?
Also make sure your new battery is clamped snugly in place. For a battery
to rattle around shortens its life.
Al Grayson