Corrosion Investigation of Chromium Nitride and Chromium Carbide Coatings for PEM Fuel Cell Bipolar Plates in Simulated Cathode Condition

Abstract

Abstract Transition metals nitrides and carbides are used as coatings on bipolar plates for proton exchange membrane fuel cells (PEMFCs) due to their suitable electrical conductivity and corrosion resistance. Chromium electroplated AISI 316L stainless steel bipolar plates were treated by plasma nitriding and solid carburizing to form chromium nitride and chromium carbide, respectively. The presence of CrN/Cr 2 N and Cr 7 C 3 /Cr 23 C 6 was verified by X‐ray diffractometry (XRD) in chromium nitride and chromium carbide coatings, respectively. The corrosion behavior of coatings was investigated by potentiodynamic polarization, potentiostatic polarization and electrochemical impedance spectroscopy (EIS) in simulated cathode condition. Coated samples showed better corrosion behavior than untreated bare sample. EIS results indicated decrease in corrosion current density after 500 hours, however coatings acted as barrier against solution access to substrate. Corrosion current densities of coatings were close to targets of United Stated department of energy (DOE).