seal is then removed and a permanent weld joint is made about the flanged area 22 with reference to fig2 a bipolar plate assembly 34 further includes an optional spacer plate 32 disposed between a first plate 36 and a second plate 38 with additional flow paths for coolant there between when the spacer plate 32 or similar element is positioned between plates 36 38 each plate of the pair must be welded to the spacer plate 32 as best seen in reference to fig4 a plurality of coolant apertures 40 are disposed in the spacer plate 32 to ensure that a fully turbulent flow of coolant exists between the two plates 36 38 a plurality of reactant gas ports 42 are also identified which provide inlets or outlets for reactant gas flow to each of a plurality of channels 44 formed in the face of the plates 36 38 in the embodiment shown in fig2 to form the bipolar plate assembly 34 a first plate flange 46 is aligned with a second plate flange 48 and the two flanges are preferably welded all interface areas between reactant gas channels or ports and the coolant volume are similarly welded the welded joints can be formed by any welding method provided the permanent seal surrounds the coolant volume as well as the plate perimeters if a temporary joint is formed between the first plate flange 46 and the second plate flange 48 a seal 50 is disposed between the first plate flange 46 and the second plate flange 48 and the two plates 36 38 are butted all interface areas between reactant gas channels or ports and the coolant volume are similarly sealed the.