Identifying high voltage plates in air purifier

Hi all, I have a series of plates from a fairly large air purifier that had 6000 Volts going through it! The plates are 24" by 32" and 5 mil thick. I can not figure out what they are..look like aluminum (not with that voltage),maybe white brass? They were arranged like a battery with spacers of the same material, now the strange part..they have a bit of the "ring" of silver. Its all non-magnetic. I will get a pic over the next to days. Anyone scrapped one out before? New one for me after 30plus years! Thanks

The ones I've torn apart were always stainless steel. They were popular back in the 60's and 70's in a lot of homes in my area.