Investigation of the electrical properties and corrosion resistance of TiN coating deposited by reactive sputtering on the titanium bipolar plate, used in polymeric fuel cell

The effect of titanium nitride film on the properties of titanium bipolar plates used in polymeric fuel cell was investigated in this research. TiN coatings was deposited on the Ti-grade 1 substrate by using DC-sputtering method. Pure titanium was used as target and coating deposition was done in argon and nitrogen atmosphere. Different TiN thickness was developed by changing sputtering time. The interfacial contact resistance (ICR) between coated titanium plates and gas diffusion layer was determined by contact testing method. The electrochemical corrosion behavior of the titanium and coated samples was monitored by potentiodynamic polarization technique in 0.5 M H2SO4 at 70 ˚C. Phase identification, morphology, and microstructure of coatings were investigated by grazing incident XRD (GIXRD) and FE-SEM. The results show that TiN was developed on the Ti- plate as a major phase after coating process. Minimum value of ICR was 33 mΩ.cm2 for 0.6 µm TiN thickness which indicates that oxide layer does not form on the TiN surface. Tafel curves show that corrosion potential was promoted from -0.214 V to -0.102 V and corrosion current density decrease from 6.29 µA/cm2 to 1.83 µA/cm2 by increasing TiN thickness.