Is an alcohol-based spray cleaner ok for cleaning an aluminum heat exchanger?
When aluminum metal is exposed to the oxygen of the air at room temperture, it forms a protective air-tight layer of aluminum oxide. So as long as nothing is present that will disrupt the oxide layer on aluminium it is OK for aluminium at 20 oC to be in contact with air.

If an aluminium alkoxide is exposed to water then the aluminium alkoxide will react with the water to form aluminium oxide and the alcohol. So in alcohol which contains some water it is not possible for the aluminium to dissolve in the alcohol.

But if the alcohol is anhydrous then it will be able to enter a scratch in the aluminium and start to react with the metal thus causing corrosion. For titanium that anhydrous methanol is very corrosive.

So as long as some water is present and air is present then at room temperture