Research Information System
Renewable Energy Research Conference – Technoport 2012, Trondheim, Norway, 16 - 18 April 2012, pp.1-38
Bipolar plate is one of the critical components in polymer exchange membrane fuel cell systems (PEMFC) as it constitutes big chunk of total stack weight and stack cost. Stainless steels, among other various materials, are considered as the prominent choice of the bipolar material due to their inherent characteristics satisfying the requirements of PEMFC bipolar plates, such as mechanical support and strength to stack, flexibility, high heat, and electrical conductivity as well as chemical stability. Moreover, their forming into complex shapes can be performed conveniently at reasonable cost levels. Nevertheless, they are prone to corrosion under typical fuel cell working environment, and increased contact resistance may thus, arise.
A series of investigations, therefore, were performed to reveal the effects of several parameters on the contact and corrosion resistance of bare and coated metallic bipolar plates. These parameters included material type (SS304, SS316L, SS430, Ni270, Ti Grade I and II), forming method (e.g. stamping, and hydroforming), process condition (stamping force, speed, hydroforming pressure, rate) etc. Results, mostly conforming to reported findings in the literature, indicated that both corrosion and contact resistance performances are not at desired levels set by U.S. Department of Energy. A second set of studies was then conducted on PVD coated bipolar plates with SS316L as material of choice. Effects of coating type (TiN, CrN, ZrN), coating thickness (0.1, 0.5, 1.0 µm), forming method, manufacturing sequence (forming then coating vs. coating the blanks then forming into bipolar plate), corrosion test type (potentiodynamic and potentiostatic), and test condition (anodic, cathodic conditions), corrosion exposure on interfacial contact resistance (ICR) were evaluated at this stage. Coatings performed differently as ZrN was found to be the best in terms of corrosion resistance satisfying the DOE target and followed by CrN and TiN while TiN was the best performed in ICR tests yielding the lowest contact resistance. Apart from contact and corrosion resistance, a tribological effect study on long-term manufacturing of bipolar plates was also performed.