Fink (Jul 31, 2001 11:03 p.m.):
It is not O2.
I have a Ph.D. in organic chemistry.
All I had was high school chemistry which I now barely recall. I do recall that it was kind of interesting because it touched somewhat on reality, unlike everything else in high school. Anyway, I expected the answer to be that nothing much happens; the equilibrium would be such that small traces of the obvious compounds would form, but that would take a long time.
Although my knowledge of chemistry is very basic, the stability of aluminum oxide is such that getting it to react much is a well known story in the history of chemistry. Plus, water hardly dissolves it at all, so getting radicals to form that way gets you almost nowhere. Early chemists deduced the existence of aluminum in compounds, but the elaborate steps needed to free the metal made it far more expensive than gold. Finding that vinegar readily reacts with aluminum oxide is a surprise to say the least.
Vinegar being an acid, it might attack the aluminum, but because of aluminum's affinity for oxygen it would seem anything that got started that way would end up with the aluminum combining with the oxygen in the air instead. In the process some aluminum might be dissolved from the surface.
Still, real chemistry often proceeds differently than high school theory. My chemistry teacher had a doctors degree and frequently informed us that what we were learning was NOT real chemistry, which was ORGANIC chemistry. One day he became so exasperated with the text book that he decided to demolish the theory with a demonstration. He mixed the usual base and acid together and did not get the chemical salt and water that was predicted. You could tell that because the stuff was a different color than what you were supposed to get. Plus it gave off some noxious gas that the teacher wanted to keep us away from. (chlorine?)
So, I was really wondering what actually happens, rather than what might happen in theory.
If vinegar dissolves the oxide off aluminum, you could save yourself some work by doing that before you lap you HS, because aluminum oxide is very tough, while aluminum is not. Aluminum oxide is the second hardest naturally occurring substance, one tenth the hardness of diamond. Common sandpaper is usually aluminum oxide, although you sometimes see some with flint or garnet. Wet sandpaper is usually silicon carbide, which is nearly as tough as aluminum oxide, I believe.