Original: Wikipedia
One of the potential drawbacks of using high concentrations of methanol (and other alcohols like ethanol) in fuel is its
corrosivity to some metals, particularly
aluminium. Methanol, although a weak acid, attacks the oxide coating that normally protects the aluminium from corrosion:</p><dl> <dd>6 CH<sub>3</sub>OH + Al<sub>2</sub>O<sub>3</sub> → 2 Al(OCH<sub>3</sub>)<sub>3</sub> + 3 H<sub>2</sub>O</dd></dl>
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:</p><dl> <dd>6 CH<sub>3</sub>OH + 2 Al → 2 Al(OCH<sub>3</sub>)<sub>3</sub> + 3 H<sub>2</sub></dd></dl>
This reciprocal process effectively fuels corrosion until either the metal is eaten away or the concentration of CH<sub>3</sub>OH is negligible. Concerns with methanol's corrosivity have been addressed by using methanol compatible materials, and fuel additives that serve as corrosion inhibitors.
Though in 55 yrs or so playing with model engines, I have never seen any evidence of aluminum corrosion from methanol?</p>