Hi.

Can the surface oxide layer be permanently removed if a piece of the metal is scraped while submerged in oil -and kept in it- ?

yes, IF the oil is free of water and oxygen, but that`s harder to do than it sounds.

No, because Al reacts with water to give the oxide and hydrogen.

Thanks for the responses...

Do you know of any oil type with a low amount of reacting oxygen / moisture that you can recommend, please? or process to de-oxygenate it ? Heating it up to evaporate moisture ?

I`d probably opt for a reasonably long chain alkane (reagent grade) anywhere between Decane and Paraffin.

and add pure calcium metal to it, and just leave it stand in a desiccator for a few days.