PVD Coatings for Lightweight Bipolar Plates

Bipolar plates are one of the main components of proton exchange membrane fuel cells (PEMFCs). Their functions include distributing reactants, supporting the cell, and conducting heat and electricity. They account for a significant proportion of the fuel cell stack’s weight and volume. The main materials currently used for bipolar plates are graphite and stainless steel. Aluminium has a much lower density than steel and is easier to form than both steel and graphite. Its use, therefore, would allow fuel cells with higher power densities but is hindered due to it being prone to corrosion. This work focused on the development of corrosion-resistant and conductive coatings to address this issue. Carbon coatings with Ti and Cr adhesion layers were deposited on aluminium substrates using closed-field unbalanced magnetron sputtering. These coatings were tested for corrosion properties and performance on the cathode side of a single-cell fuel cell. Coated aluminium samples were also tested for their ability to maintain their corrosion protection after being formed. Coating with a Cr adhesion layer outperformed that with a Ti adhesion layer in both forming and fuel cell tests, demonstrating much lower performance degradation after accelerated stress testing.