Aluminium as plates is certainly an interesting experiment.
You would need to set it up so that you Do Not use electrolyte.
Very close gap, High freq pulsing, not sure if Anode or cathode??
I would try Nickel for the other plate. You would have to check the
Galvanic potential and I think cast iron may be even better with Nickel.
.
I Use nuetral plates in my efficient Hyd/Booster.
http://waterfuelcell.org/phpBB2/viewtopic.php?t=128
I just changed to KOH electrolyte - so need to do another quantity
output test. But its certainly Better = More Power.!
Very Low current draw but still with Decent Hyd/Oxy output.