Microscopic analysis on high corrosion-resistant metallic nitride-coated metallic bipolar plate for PEM fuel cell application

Abstract

To extend the durability of stainless-steel bipolar plates in proton exchange membrane fuel cells (PEMFCs), a high corrosion resistance titanium nitride (TiN) coating was deposited using cathodic arc-physical vapour deposition (CA-PVD). Optimized pre-processing conditions and deposition parameters enabled the synthesis of multi-layered TiN in a single-step process, eliminating the need for adhesion or additional layers. The incorporation of secondary elements such as oxygen and the creation of nitrogen-rich sites within the coating matrix significantly enhance the corrosion resistance. Long-term studies reveal that the coating retains its structural integrity even after 3000 h of immersion in a simulated PEMFC electrolyte under periodic potential application. Atom probe tomography (APT) analyses microstructural changes at the atomic level to investigate the role of secondary element incorporation in the corrosion resistance of the TiN coating. APT analysis reveals the presence of secondary interfaces, which promote the formation of disordered columnar structures, effectively hindering electrolyte penetration to ensure prolonged corrosion resistance throughout the testing period. This study demonstrates the effectiveness of multi-layered TiN coatings in enhancing the longevity and reliability of bipolar plates for PEMFC applications.