Johnny, I would have to imagine that a copper tank would be fine, but exspensive. And do you really need it ? Ethanol doesn't hurt normal mild steel, only the terneplated stuff. The stations around here ( SW Michigan ) that sell E85 use the same tanks and hoses and pumps that were previously used for gasoline. Thus far, there haven't been any noticeable problems. Some localities have noticed pitting on the aluminum fuel nozzles. It seems that the ethanol that splashes on the nozzle keeps things spectacularly clean, and then atmospheric mosture pits the nozzle before the aluminum can form a self protecting coating. Nozzles that have been nickle plated solved the issue. I plan on useing unpainted and unplated steel tanks and watching them to see if anything happens. I have aluminum tanks I may try as well, still contemplating. Whichever tanks get used, they will have ground straps added, as ethanol is an electrical conductor. DF, @ work on lunch