Solution acidity and temperature induced anodic dissolution and degradation of through-plane electrical conductivity of Au/TiN coated metal bipolar plates used in PEMFC

A novel composite coating of gold/titanium nitride on stainless steel (Au/TiN/SS) was developed by introducing Au dots onto a TiN coating to improve the corrosion resistance and electrical conductivity of stainless steel bipolar plates for the polymer electrolyte membrane fuel cell (PEMFC). The effects of temperature and pH on conductivity and corrosion resistance of the Au/TiN/SS in a simulated PEMFC environment were investigated. The results showed that the interfacial contact resistance of TiN coating reduced from 5.48 mΩ cm 2 to 1.72 mΩ cm 2 after introducing the Au dots, indicating that Au dots can enhance the interfacial conductivity of the composite coating on stainless steel. The increases of solution temperature and acidity enhanced the dissolution of TiN as well as the delamination of Au dots from the composite coating, and the corrosion current density (i corr ) of Au/TiN coating increased in high temperature and strong acidic environments. The thin layer of TiN x O y and TiO 2 around the Au dots was preferentially dissolved to detach the Au from the composite coating, therefore induced the degradation of through-plane electrical conductivity of the Au/TiN coated metal bipolar plates. • A coating with high corrosion resistance and good electrical conductivity was developed. • The interfacial contact resistance reduced by two thirds after introducing the Au dots. • Solution acidity and temperature induced degradation of coating was particularly analyzed. • Dissolution of TiN x O y and TiO 2 induced the conductivity degradation of Au/TiN coating.