High temperature combustion creates all sorts of species...
Hydrocarbons that are pure carbon and hydrogen don't JUST do water and CO2, they create CO, NOx of various species, and HC...things that shouldn't, but due to high temperature equilibrium, they are made and they exist.
Alcohols create aldehydes and the like, so will also be creating Acetic Acid. It will be anhydrous, and gaseous, so not much water to make it a problem (98% sulfuric lives in carbon steel tanks...no water to make it exceptionally corrosive, but don't get on your skin).
Doubt it would make it past the converter, or be much of a problem after shutdown.
Is a problem in underground tanks where acetobacteria eat the ethanol, create acetic acid (Ethanoic Acid), and start destructing things.