Erm... Alumina basically IS fancy corroded aluminium right? Thats like saying that rust will never rust (which ofc in a way is true).
However, about the whole metal cap thing.... i think i really need to type on a board with all metal caps one of these days because i have a feeling that it could suck quite a bit if you're a very fast typer (mass being slow and everything). Anyone here have some experience with long/fast typing on full metal?
It's a ceramic: no longer a metal Al2O3. You could say that it's oxidized aluminum, but so is sapphire:
https://en.wikipedia.org/wiki/Sapphire(chemical formula of sapphire as Al2O3).
Alumina is closer to Corundum in it's crystalline form, which is cool 'cause it has a mohs of 9.
It's pretty awesome:
https://en.wikipedia.org/wiki/AluminaAnyway it's oxidized aluminum, not corroded aluminum. One main reason it's so good about corrosion, etc is because it's already oxidized (so your rust will never rust is at least partially true!). On main difference is that iron oxide is fail whereas aluminum oxide is win. I love ceramics.