I had an aluminium tank that had developed a line of corrosion holes in the bottom of one side which were in conjunction with the gum that forms when modern fuel is allowed to evaporate in-situ. The corrosion holes were under the gum. I suspect that there may have been some water also present during the hole-forming process but by the time I got the tank it was dry and just had the gum and the holes.
If you don't allow things like that to happen to the tank, aluminium is one of the best (longest-lasting and lightweight) materials for a fuel tank. I've seen zero corrosion damage on any other aluminium trials bike fuel tank.