Well, that raises an intresting point. I did some brief reconnaissance on rads and they all appear to have copper tubes in them. Maybe it was just the few i looked at. Anyway, that reservoir is extruded aluminum. Problem? Does the anodizing protect the metal and stop the reaction?
Also, what wattage peltier would best suit this? Ebay has peltiers as low as 43 watts. Off my judgment, i would asume a 90watt peltier would be ideal. I am however no expert.