Corrosion resistance of CrN film deposited by high-power impulse magnetron sputtering on SS304 in a simulated environment for proton exchange membrane fuel cells

Insufficient corrosion resistance and conductivity are two major problems hindering the wide application of stainless steel (SS) bipolar plates in proton exchange membrane fuel cells. This study explores the use of CrN monolayer and multilayer films to improve the performance of SS304 bipolar plates, which are realized by high-power impulse magnetron sputtering with single pulse width or alternating pulse width. The effect of pulse width on the film structure and composition was characterized by various characterization techniques. Furthermore, corrosion and interfacial contact resistance (ICR) test results show that monolayer CrN film using a single long pulse of 40 μs has the lowest corrosion current density of 0.08 μA/cm2 (0.6 V vs. Ag/AgCl) and ICR of 3.15 mΩ cm2 in all coated samples. As the pulse width increases, vacancy-like defects in film decrease and the density increases, which is attribute to high bombardment flux and high average power of long pulse during deposition.