[NC_ME]

Bear with me, I am new to the forum and do not have a strong chemistry background.
I have been researching the reaction of sodium hydroxide with Al and Al alloys.  I understand that Al will react with sodium hydroxide/water solution to produce sodium aluminate and hydrogen gas:
2Al + 2NaOH + 2H2O -> 2Na(AlO2) + 3H2
I also know that it can create an aluminium hydroxide ion:
2Al + 2NaOH + 6H2O -> 2Na(Al(OH4)) + 3H2
I know this is the case for aluminium oxide as well:
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH4)) + 3H2
Everything I have researched indicates this is the case for immersion in NaOH solutions.  What happens if a free oxygen molecule is introduced, such as if the sodium hydroxide is sprayed onto the Al?  I have not been able to find a plausible reaction.  Perhaps the free oxygen does not react?
2Al + 2NaOH + 2H2O + O2 -> 2Na(AlO2) + 3H2 + ?
I am conducting some research in anticipation of a possible experiment with both immersing and spraying aluminum samples with low concentration of sodium hydroxide (pH 10-12).  I know the low concentration may not produce much, but that is one of the constants with which I am working.  The experiment would be more fun with a higher concentration, but due to the requirements, that is what the experiment will use.
Thoughts?
Thanks in advance.

[Borek]

I know this is the case for aluminium oxide as well:
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH4)) + 3H2

It is not balanced - and not without a reason. The reaction doesn't look the way you wrote it.

Na(AlO2) and Na(Al(OH4)) are in a way the same compound, differing by the hydration state.

Al is already covered with the oxide layer. When you add NaOH solution it first dissolves the oxide, then attacks the metal. Oxygen presence doesn't change much.

[Arkcon]

Everything I have researched indicates this is the case for immersion in NaOH solutions.  What happens if a free oxygen molecule is introduced, such as if the sodium hydroxide is sprayed onto the Al?  I have not been able to find a plausible reaction.  Perhaps the free oxygen does not react?
2Al + 2NaOH + 2H2O + O2 -> 2Na(AlO2) + 3H2 + ?

I'd never heard of oxygen participating in this particular reaction.  I suppose it could, i don't know everything.  But if you chemistry background is't strong, I don't think its too unfair for me ask, "Did you just make up this reaction?"  Just because you think its plausible, doesn't mean it is.

Remember, most simple chemical reaction occur on the surface of the Earth.  If humans are around, and they're not dying, oxygen will be present.  If so someone should have noticed such a reaction by now.

I am conducting some research in anticipation of a possible experiment with both immersing and spraying aluminum samples with low concentration of sodium hydroxide (pH 10-12).  I know the low concentration may not produce much, but that is one of the constants with which I am working.  The experiment would be more fun with a higher concentration, but due to the requirements, that is what the experiment will use.
Thoughts?
Thanks in advance.

I'm wondering what direction you plan to go with this.

[Zyklonb]

Other than hydrogen, everything is in it's most stable oxidation state and thus cannot be further oxidized.
Kinetics for hydrogen's oxidation will not allow it to combine under these conditions without sufficient activation energy (eg. a spark).
BTW, although it may not sound like a big difference, pH 10 and pH 12 differ in NaOH conc a heckofa lot, you might want to be more specific.

[NC_ME]

I know this is the case for aluminium oxide as well:
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH4)) + 3H2

It is not balanced - and not without a reason. The reaction doesn't look the way you wrote it.

Na(AlO2) and Na(Al(OH4)) are in a way the same compound, differing by the hydration state.

Al is already covered with the oxide layer. When you add NaOH solution it first dissolves the oxide, then attacks the metal. Oxygen presence doesn't change much.

  I put the parentheses in the wrong place. Should have been:
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH)4) + 3H2

I'd never heard of oxygen participating in this particular reaction.  I suppose it could, i don't know everything.  But if you chemistry background is't strong, I don't think its too unfair for me ask, "Did you just make up this reaction?"  Just because you think its plausible, doesn't mean it is.

Remember, most simple chemical reaction occur on the surface of the Earth.  If humans are around, and they're not dying, oxygen will be present.  If so someone should have noticed such a reaction by now.

I'm wondering what direction you plan to go with this.

It is fair to ask... yes, I made it up. Although there should be some free oxygen in a NaOH/water solution, it should be less than spray in air (i.e. larger volume of air contacts the Al sample with spray). I wondered if there could be further reaction to the oxygen. If it isn't plausible, that's fine, that's why I am asking. 

As for pH 10 to pH 12, I understand. I am specifically looking at pH 10.5, but it's possible the experiment may include a large range to observe different reactions. (10.0, 10.5, 11, 11.5, 12)

Thanks for all the responses.

[Enthalpy]

Just experiment.

But most importantly, observe with the same aluminium alloy that you plan to use in the future. The behaviours of, say, a bicycle tube and a foil to wrap food are completely different.

[Borek]

  I put the parentheses in the wrong place. Should have been:
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH)4) + 3H2

It is not a problem with parentheses. Besides, what you wrote now is exactly the same thing you wrote earlier:

I know this is the case for aluminium oxide as well:
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH4)) + 3H2

Try to balance this reaction both with hydrogen being produced and without hydrogen being produced. Only one of them can be balanced, which is a clear sign one of them can't happen.

[NC_ME]

  I put the parentheses in the wrong place. Should have been:
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH)4) + 3H2

It is not a problem with parentheses. Besides, what you wrote now is exactly the same thing you wrote earlier:

I know this is the case for aluminium oxide as well:
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH4)) + 3H2

Try to balance this reaction both with hydrogen being produced and without hydrogen being produced. Only one of them can be balanced, which is a clear sign one of them can't happen.

Ok. Sorry again. H2 would not be produced. 
Al2O3 + 2NaOH + 3H2O -> 2Na(Al(OH4))

[Borek]

Do you understand why there will be no hydrogen produced, when the Al is in the form of the oxide?

[NC_ME]

Well I understand that my initial reaction was not balanced (showing alum oxide produced hydrogen gas). I made the error of copying the first reaction with elemental aluminium but not removing the "H2"

I do understand that all chemical reactions must be balanced (although due to my copy/paste errors you could easily argue otherwise), but as to why the oxidized state of aluminium does not produce H2 gas, I am not sure. Don't both reactions cause the decomposition of water? i.e. the Al ion attracts the OH ion.

Do other oxidized amphoteric metals react in a similar manner? i.e. oxidized state does not produce H2 gas but elemental metals do?

You are all helping me to learn as I go. Thanks again.

[Zyklonb]

The reason is because when hydrogen bonds to oxygen, it gives an electron, that is called oxidation. but when the aluminum reacts, it has an even weaker affinity for electrons (it wants to get rid of them more than the hydrogen does), but the electrons need to go somewhere, and oxygen certainly won't take anymore. So hydrogen gets them back, and turns into elemental hydrogen gas.
This is called a single replacement reaction.
In the case of the aluminum oxide, Al has already lost it's electrons to oxygen, and thus doesn't have to give any to hydrogen.