Investigation on application of Cr and Ti interlayer to improve corrosion resistance of titanium carbide coated metallic bipolar plates for PEMFCs

This research investigated the effects of chromium (Cr) and titanium (Ti) interlayers on the improvement of the corrosion resistance and electrical conductivity of titanium carbide (TiC) coatings used in metallic bipolar plates for polymer electrolyte membrane fuel cells. Micro-defects were observed on the surfaces of Cr/TiC- and Ti/TiC-coated specimens. In particular, the Cr/TiC coated specimens exhibited a higher defect density than the Ti/TiC coated specimens due to the low lattice compatibility of Cr and TiC. However, a 1:1 concentration ratio of Ti to C enabled crystallographic and electrochemical stability in the specimens. The application of the Cr interlayer improved corrosion resistance and caused significantly smaller variations in current density with fluctuations in potential. In particular, at high potentials, the Cr/TiC-coated specimens exhibited a significantly lower current density. The Cr interlayer had a greater influence on the improvement of corrosion resistance. Notably, the crystallographic properties of TiC exerted more considerable effects on the corrosion resistance of the coated specimens than the density of defects formed on their surfaces.