When would I use aluminum components (gate valves etc..) in a vacuum chamber over stainless or vice versa?

Question

I've just started searching for an 8" conflat gate valve for a vacuum deposition chamber (PVD sputtering with Ar process gas). I've realised that there are now Aluminum gate valves as well as Stainless valves that I'm used to. Can someone tell me which applications require which valve or what the consierations for use of either would be.
Many Thanks,
Steve

Answer 1

Is one significantly cheaper? That might be the main consideration. I feel that stainless would have a longer operating life. The only consideration I could think of is that, although stainless is not that ferromagnetic, if you are concerned about affecting B fields (around your sputtering gun, say) then go aluminum. I think stainless is still the status quo. Aluminum tends to be brittle, even if it is much lighter.