Originally Posted by
gyozadude
Windex and most glass cleaning solutions contain ammonia. Others suggested ammonia above and I've used this before with exactly your problem, although I think the liquid did more lubrication than ammonia did clearing the oxide layer. I still ended up with big scratched seat post after muscling it out. If the seat post was stuck in a steel frame, I'd recommend using coke/pepsi and letting it sit all night. It contains phosphoric acid which reacts and loosens rust. I guess know your chemistry and read labels on household products!
there was some crazy guy on here before who poured some ammonia onto his aluminum tabbed, aluminum steerer carbon fork because he was trying to loosen a stuck stem. No surprise, but the aluminum tabs were dissolved enough that they wiggled in the fork.
I'm guessing the Al2O3 and Al reacts with dissociated ammonia, NH4+ or NH2-, which then becomes AlN, Al(NH2)3, H2, H2O, O2 or something to that nature. I haven't seen any good documentation of what reaction actually takes place, but I doubt ammonia only eats the aluminum oxide top layer, because aluminum is quite high on the reactivity series, which makes it fairly weak against acids.