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Study on dimensional and corrosion properties of thixoformed A356 and AA7075 aluminum bipolar plates for proton exchange membrane fuel cells

Bolouri, Amir; Kang, Chung Gil

Authors

Amir Bolouri Amir.Bolouri@uwe.ac.uk
Associate Professor in Manufacturing

Chung Gil Kang



Abstract

Metallic bipolar plates for polymer exchange membrane (PEM) fuel cells are currently manufactured by stamping of thin sheets. However, there are dimensional and shape errors of microchannels because of forming limitation such as spring back of thin sheets after stamping. On the other hand, stamping process is limited to commercially available sheetalloys, which restricts the development of a high corrosion resistant substrate aluminum alloy. Here, thixoforming (a commercial semisolid route) that is applicable to a wide range of aluminum alloys is proposed for net-shape micromanufacturing of aluminum bipolar plates with high dimensional stability. High corrosion resistance cast A356 (Cu-free) and wrought AA7075 (~2% Cu) aluminum billets are used for this study. Initial billets are heated at different semisolid temperatures. Subsequently, the semisolid slurries are injected into the die cavity. A356 and AA7075 aluminum bipolar plates are successfully fabricated by thixoforming with very small deviation of 0.7% and 1.5% from the nominal value of 0.300mm in the microchannel depth, respectively. A multilayer coating of TiN/CrN is deposited on the surface of thixoformed bipolar plates through a commercially available magnetron sputtering technique. Electrochemical corrosion tests show that coated-thixoformed A356 (Cu-free) bipolar plates have significantly lower corrosion current densities than coated-thixoformed AA7075 (~2% Cu) bipolar plates. This seems to be due to the deleterious effect of Cu alloying element on the corrosion resistance of aluminum alloys that clearly confirms the importance of substrate material development for corrosive PEM fuel cell environment. It is suggested that specific high corrosion resistance aluminum alloy for PEM fuel cell application can be simply designed and then thixoforming can be efficiently and cost effectively employed to fabricate net-shape aluminum bipolar plates. © 2014 Elsevier Ltd.

Journal Article Type Article
Acceptance Date Jun 12, 2014
Online Publication Date Jul 5, 2014
Publication Date Nov 1, 2014
Journal Renewable Energy
Print ISSN 0960-1481
Electronic ISSN 1879-0682
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 71
Pages 616-628
DOI https://doi.org/10.1016/j.renene.2014.06.021
Keywords aluminum bipolar plate, dimensional stability, corrosion property
Public URL https://uwe-repository.worktribe.com/output/823322
Publisher URL http://dx.doi.org/10.1016/j.renene.2014.06.021