When you are using chemicals/electrolyte to do electrolysis, you have a chemical reaction going on inside the cell. If you listen to the electrolysis crowd on youtube they say 316 ss is better than 304 because it has more of something fancy and less of something else. but this is for exposure to a chemical reaction
When you use high voltage, it is a physical process of opposite electrical attraction, so the only "exposure" going on is simply the contact of the water/hydrogen/oxygen against the ss, so there is no chemical reaction to be contained.
316 ss is not needed for high voltage, simply because there is no chemical reaction, it is a physical process, and the 304 ss is cheaper (law of economics) and is still inert to the process.
As for copper. in a high voltage situation exposed to water, hydrogen, and oxygen, i don't personally know of any effects/reactions they will have with the copper, but i would guess it would be minimal.
As for copper. In a electrolytic environment, you are exposing the copper to a chemical reaction with potassium/sodium as well as water, hydrogen, oxygen, and i am not sure what the reaction with potassium/sodium is with copper, it my be perfectly inert to the process. I will ask some chemistry friends about it and see what they think. Stan says that even some types of platinum will erode in this process too, so that lends to the idea something vicious is going on in a electrolysis cell.
As long as you are having good (or bad! since we learn from those too) results then keep it up
I just wanted to outline the differences between some common thoughts about materials as i have come to learn.
