Investigation of multi-coating process treated magnesium alloy as bipolar plate in polymer electrolyte membrane fuel cell

• Magnesium alloy is coated by electroless Ni coating and PVD carbon film.
• Ni + C coating exhibits the best corrosion resistance among these coatings.
• Ni + C coating has the lowest ICR of 2.97 mΩ-cm2 at compaction force of 150 N cm−2.
• Further improvement in corrosion resistance is required for magnesium alloy.

Magnesium alloy bipolar plates offer great advantage in weight reduction of polymer electrolyte membrane fuel cell. An attempt to improve the corrosion resistance and surface conductivity of magnesium alloy has been made by a medium electroless plating Ni coating prior to PVD deposition of carbon film, envisaging the application of these coating/substrate systems as bipolar plate in PEMFC. The results show that Ni + C coated magnesium alloy GW83 has the best corrosion resistance of 8.65 μA cm−2 and 0.80 μA cm−2 in the simulated cathodic and anodic environments. The release of metallic ions is also greatly inhibited by Ni + C coating. The interfacial contact resistance (ICR) of the magnesium alloy GW83 is decreased from 196.5 mΩ-cm2 to 2.97 mΩ-cm2 by Ni + C coating at the compaction force of 150 N-cm−2. After potentiostatic tests, Ni + C coated sample has the lowest ICR of 15.6 mΩ-cm2 and 52.6 mΩ-cm2 in the anode and cathode environment, respectively.