What can I use as a sacrificial electrode to stop the oxidation of aluminium?
I think that you are interested in the corrosion protection of aluminum. You have basically two choices depending on your experiment setup.

You can use an impressed current protection or a sacrificial anode method. The sacrificial anode method uses a more reactive metal (less noble) in contact with the metal requiring protecting. The less noble metal reacts first within corrosive environment.

The impressed current protection uses electric current to charge the metal requiring protecting with excess electrons. It changes the electrode potential in the negative direction until the metal is not reacting.

If you want to use the sacrificial anode method look in the table where you are looking for metal that is positioned higher than your aluminium (is more electronegative - so non of the mentioned metals).

More useful information can be found here CORROSION PROTECTION OF METALS 
 or here metals.about.