Corrosion Resistant Al-Cr-Mo Alloy Coating on Type 316L Stainless Steel Bipolar Plates for Proton Exchange Membrane Fuel Cell Applications

The most important issues that plague wider use of polymer electrolyte membrane fuel cells (PEMFCs) are insufficient corrosion resistance, electrical conductivity and wettability of metallic bipolar plates (BPPs). To address these issues, an amorphous Al-Cr-Mo ternary alloy coating is applied on type 316L stainless steel using direct current magnetron sputtering. The electrochemical corrosion behavior of bare and alloy coated specimens has been investigated by polarization and electrochemical impedance spectroscopy techniques under simulated fuel cell working environment consisting of 0.5M H2SO4 at 70 +/- 2 degrees C. The results indicate that the corrosion current density of the alloy coated specimen is approximately 0.2 mu A cm(-2) showing a reduction of two orders of magnitude. The polarization resistance increased by an order of magnitude and the interfacial contact resistance (ICR) is reduced significantly (45 and 48 m omega cm(2) in the simulated anode and cathode environments, respectively) due to the application of the coating. The chromium and molybdenum enrichment on the surface of coated specimen, as revealed by X-ray photoelectron spectroscopy, is proposed to be responsible for the improved corrosion resistance. Further, the coating is expected to show significantly better water management due to high hydrophobicity than the bare stainless steel.