Alcohol will corrode aluminum. It leaves the little white "fuzzies" on the surface (aluminum alkoxide). This is an inorganic salt and should be totally captured in a fuel filter. However, I have never seen this in an alloy tank using modern alcohol containing fuels. Perhaps there isn't enough alcohol in most gas formulations to worry about. If I were using an alloy tank in an area with alcohol blended gasoline, I would definitely drain it before storing it for the winter, but I don't think I would be overly concerned during the riding season.
Has anyone experienced problem with corrosion of the float bowls in Mikuni carbs? They are aluminum also. I haven't heard of any issue with them. (At least not issues related to alcohol corrosion).