aluminium alloy tanks

Have 6 bikes with aluminium tanks. None affected.

I have two Norton's with Aluminium tanks, but run on E0 fuel.

I wouldn't like to try it on E10....You might not have a choice before long?

E15 or higher for that matter.

There are two fuel related issues with tanks:

1. the material used to construct the tank might be affected by petrol and any additives in it. This is the case with fibreglass. Petrol hardens the plastic resin over time, making it more suceptible to damage. More relevant to today, ethanol disolves the resin leaving the tank severely weakened and prone to leakage. And it does this quite quickly. This is not a concern for steel or aluminium tanks, although the material used for seals around taps and filler should be considered.
2. moisture from the air can condense in the tank causing corrosion. This will happen over time regardless of the fuel used but is exacerbated by enthanol which actively draws water from the air over and above normal condensation. This is a particular problem with steel tanks which will rust thru. Aluminium is much better in this regard and GRP, ironically, is quite impervious.

With an aluminium tank, if you use the bike from time to time and fill with fresh fuel a couple of times a year you will not have any issues, regardless of ethanol content. But if you will leave the vehicle standing for years it would be advisable to drain and dry the tank. I.e. same procedure as for carburettors.