[NewCandle] Anodizable metals and essential conditions for glow discharge?

[Keith Nagel]

Hey Nick + Horace,

You got me to wondering about other metals. A quick survey of
capacitor manufacturers yielded this list of candidates.

aluminum, niobium, tantalum, titanium, tungsten, zirconium.

I know we've tried the first and last, but how about the others?
Anyone? Is glow unique to aluminum? Of course, disruptive discharge
due to dielectric failure would be seen on all of them, as
Nick described with zirconium. If it is unique to aluminum,
perhaps the reason is that you need the porous
structure to see glow. That would be a good question to answer
with the scope. If you can get glow from Zr, is the oxide structure
porous?

K.