Metalshopteacher

I am a Highschool metal shop teacher and I want to make some crucibles for melting aluminum in and I was told that stainless steel is the best for this because of its high melting point and it wont oxidize in the foundry... What I was wondering about, does anyone know if stainless forms a scale on the surface of the metal when heated, I don't recall it doing so but have never heated it up in my forge before.