Quote from the Wiki:
"One of the potential drawbacks of using high concentrations of methanol (and other alcohols, such as ethanol) in fuel is the corrosivity to some metals of methanol, particularly to aluminium. Methanol, although a weak acid, attacks the oxide coating that normally protects the aluminum from corrosion:
6 CH3OH + Al2O3 → 2 Al(OCH3)3 + 3 H2O
The resulting methoxide salts are soluble in methanol, resulting in a clean aluminium surface, which is readily oxidized by dissolved oxygen. Also, the methanol can act as an oxidizer:
6 CH3OH + 2 Al → 2 Al(OCH3)3 + 3 H2
This reciprocal process effectively fuels corrosion until either the metal is eaten away or the concentration of CH3OH is negligible. Concerns with methanol's corrosivity have been addressed by using methanol-compatible materials, and fuel additives that serve as corrosion inhibitors."
Recall that its the oxide layer that protects the metal (just like the chromium oxide layer on stainless steel)
I also know also from first hand experience that tomato soup and its mould can eat through 1mm of aliminium saucepan in about a week
