Ex-situ evaluation of PTFE coated metals in a proton exchange membrane fuel cell environment
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Abstract
Metallic-based bipolar plates exhibit several advantages over graphite-based plates, including higher strength, lower manufacturing cost and better electrical conductivity. However, poor corrosion resistance and high interfacial contact resistance (ICR) are major challenges for metallic bipolar plates used in proton exchange membrane (PEM) fuel cells. Corrosion of metallic parts in PEM fuel cells not only increases the interfacial contact resistance but it can also decrease the proton conductivity of the Membrane Electrode Assembly (MEA), due to catalyst poisoning phenomena caused by corrosive products. In this paper, a composite coating of polytetrafluoroethylene (PTFE) was deposited on stainless steel alloys (SS304, SS316L) and Titanium (G-T2) via a CoBlast™ process. Corrosion resistance of the coated and uncoated metals in a simulated PEM fuel cell environment of 0.5 M H2SO4 + 2 ppm HF at 70 °C was evaluated using potentiodynamic polarisation. ICR between the selected metals and carbon paper was measured and used as an indicator of surface conductivity. Scanning Electron Microscopy (SEM), 3D microscopy, Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and contact angle measurements were used to characterise the samples. The results showed that the PTFE coating improved the hydrophobicity and corrosion resistance but increased the ICR of the coated metals due to the unconductive nature of such coating. Thus, it was concluded that it is not fully feasible to use the PTFE alone for coating metals for fuel cell applications and a hybrid coating consisting of PTFE and a conductive material is needed to improve surface conductivity.Citation
Olabi, A-G., Baroutaji, A., Carton, JG., Oladoye, AM., Stokes, J. and Twomey, B. (2017) 'Ex-situ evaluation of PTFE coated metals in a proton exchange membrane fuel cell environment', Surface and Coatings Technology, 323, pp. 10-doi: 1710.1016/j.surfcoat.2016.11.105Publisher
ElsevierJournal
Surface and Coatings TechnologyAdditional Links
http://linkinghub.elsevier.com/retrieve/pii/S0257897216312816Type
Journal articleLanguage
enISSN
0257-8972Sponsors
Enterprise Irelandae974a485f413a2113503eed53cd6c53
10.1016/j.surfcoat.2016.11.105
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