Corrosion characteristics and interfacial contact resistances of TiN and CrN coatings deposited by PVD on 316L stainless steel for polymer electrolyte membrane fuel cell bipolar plates

Abstract

In a polymer membrane fuel cell stack, the bipolar plate is a key element because it accounts for over 50% of total costs of the stack. In order to lower the cost of bipolar plates, 316L stainless steels coated with nitrides such as TiN and CrN by physical vapor deposition were investigated as alternative materials for the replacement of traditional brittle graphite bipolar-plates. For this purpose, interfacial contact resistances were measured and electrochemical corrosion tests were conducted. The results showed that although both TiN and CrN coatings decreased the interfacial contact resistances to less than 10 mΩ·cm 2 , they did not significantly improve the corrosion resistance in simulated polymer electrolyte membrane fuel cell environments. A CrN coating on 316L stainless steel showed better corrosion resistance than a TiN coating did, indicating the possibility of using modified CrN coated metallic bipolar plates to replace graphite bipolar plates.

Electrochemical properties and interfacial contact resistance of plasma ion nitrided titanium as PEMFC bipolar plate

“…In general, when TiN is deposited by PVD and CVD methods, pores form on the surface, which can contribute to corrosion. 27) In the case of ion nitriding, pore formation differs, depending on the gas, time, and temperature used in the nitriding process. 28,29) In the present study, no pores formed, and no corrosion-related damage was observed.…”