TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Process: The welding step is resistance welding (preferably), vibrational welding, ultrasonic welding, laser welding, heat lamination, or hot bonding techniques. Resistance welding comprises placing the mating region and complementary region in close proximity to each other, applying an electrical current at 0.1-5 (0.8-1.1) amperes/mm2 for 0.1-100 seconds and voltage of 5-25 volts between the first coolant plate and the adjacent plate to produce localized heat, and ceasing to apply current and applying pressure of 1-1000 (100-300) psig to the first coolant plate and the adjacent plate. The electric current is applied using external electrodes or the plates themselves. The vibration welding comprises applying a vibrational force at 100-500 cycles/sec for 3-100 seconds at an amplitude of 0.5-5 mm between the first coolant plate and adjacent plate, and ceasing to apply the vibrational force and applying pressure at 1-1000 (100-300) psig to the first coolant plate and the adjacent plate. Preferred Component: At least one of the first coolant plate and the adjacent plate comprise a polymer rich outer layer on the mating region and/or complementary region. The mating region and complementary region are located adjacent to the periphery of the first coolant plate and the adjacent plate. The first coolant plate and adjacent plate comprise at least one manifold hole (42) and the mating region and complementary region are at the periphery of the manifold holes. They comprise at least one flow field channel (23). The cell component has a contact resistance less than the contact resistance of two plates that are not joined together.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The polymer is thermoplastic polymer from melt processable polymers, partially fluorinated polymers, thermoplastic elastomers, liquid crystalline polymers, polyolefins, polyamides, and/or aromatic condensation polymers. Preferred Composition: The polymer is a blend of 1-30 (5-25) wt.% maleic anhydride modified polymer with the thermoplastic polymer, partially fluorinated polymers, and/or liquid crystalline polymer. The polymer rich outer layer comprises 25-100 (100)% polymer.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The conductive filler is graphite fiber or graphite powder.