Title: Increase in the corrosion resistance of stainless steel bipolar plates by the formation of thermally-induced Cr-nitride

Authors: Seok Hee Lee; Sung Pil Woo; You Na Lee; Young Soo Yoon

Addresses: Materials Research and Education Center, Auburn University, Auburn, AL 36849, USA ' Department of Materials Science and Engineering, Yonsei University, Seoul 120-749, South Korea ' Department of Chemical and Biological Engineering, Gachon University, Seongnam-si, Gyeonggi-do 461-701, South Korea ' Department of Chemical and Biological Engineering, Gachon University, Seongnam-si, Gyeonggi-do 461-701, South Korea

Abstract: Cr-nitride layer is formed on the surface of Cr-electroplated stainless steel to use metallic bipolar plates of polymer electrolyte membrane fuel cell (PEMFC). The dense and continuous Cr-nitride layer is confirmed by scanning electron microscope (SEM) results. The corrosion resistance results in aggressive environments of PEMFC reveal that the corrosion current density of 0.5 μA cm⁻² and 0.5 μA cm⁻² are presented in anodic and cathodic environments of PEMFC, respectively. The highest protective efficiency of 99.9% is recorded in the cathodic condition. The dense Cr-nitride layer provides sufficient corrosion resistance. Moreover, the interfacial contact resistance (ICR) of Cr-nitride layer is significantly decreased up to 15 mΩ cm⁻² compared with pure stainless steel and the ICR is maintained after corrosion tests. This analysis indicates that the improvement is originating solely from dense Cr-nitride layer on the surface.

Keywords: corrosion resistance; thermal nitridation; polymer electrolyte membrane fuel cells; PEMFC; bipolar plates; stainless steel; stainless steel bipolar plates; chromium nitride; interfacial contact resistance; ICR.

DOI: 10.1504/IJNT.2016.077083

International Journal of Nanotechnology, 2016 Vol.13 No.4/5/6, pp.330 - 344

Published online: 20 Jun 2016 *

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