Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates
The development of bipolar plate materials with enhanced corrosion resistance and surface conductivity is critical for the commercial application of proton exchange membrane fuel cells (PEMFCs). The corrosion behavior and surface conductivity of electrochemically nitrided 446 stainless steel with an...
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2025-05-01
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| author | Ronghai Xu Yangyue Zhu Ruigang Zhu Moucheng Li |
| author_facet | Ronghai Xu Yangyue Zhu Ruigang Zhu Moucheng Li |
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| description | The development of bipolar plate materials with enhanced corrosion resistance and surface conductivity is critical for the commercial application of proton exchange membrane fuel cells (PEMFCs). The corrosion behavior and surface conductivity of electrochemically nitrided 446 stainless steel with and without the pretreatment of Cr-enrichment were investigated in the simulated PEMFC anode and cathode environments (i.e., 0.5 mol L<sup>−1</sup> H<sub>2</sub>SO<sub>4</sub> + 2 ppm HF solution bubbled with hydrogen or air at 80 °C) using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma–mass spectrometry (ICP-MS), and electrochemical measurement techniques. Extending the nitriding time from 5 to 30 min enhances the surface conductivity but reduces the corrosion resistance. After the pretreatment and 30 min of nitridation, a thin film formed on the specimen surface, which mainly consists of Cr-nitrides and -oxides with atomic fractions of 0.42 and 0.37, respectively. The Cr-enriched and nitrided specimen shows spontaneous passivation in both the simulated cathode and anode environments and higher corrosion potentials, lower passive current densities, and larger polarization resistances in comparison with the directly nitrided specimens. Its stable current densities are about 0.26 and −0.39 μA cm<sup>−2</sup> after 5 h of polarization tests at 0.6 V<sub>SCE</sub> in the cathode environment and at −0.1 V<sub>SCE</sub> in the anode environment, respectively. Its contact resistance is about 5.0 mΩ cm<sup>2</sup> under 1.4 MPa, which is close to that of the specimen directly nitrided for 120 min and slightly decreases after the potentiostatic polarization tests. These results indicate that Cr-rich pretreatment improves not only the corrosion resistance and surface conductivity of nitrided specimens but also the efficiency of electrochemical nitridation. |
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| spelling | doaj-art-0e7ddc4abfc54d9c82241179fba3c0802025-08-20T03:14:32ZengMDPI AGMetals2075-47012025-05-0115556610.3390/met15050566Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar PlatesRonghai Xu0Yangyue Zhu1Ruigang Zhu2Moucheng Li3Institute of Materials, School of Materials Science and Engineering, Shanghai University, 149 Yanchang Road, Shanghai 200072, ChinaInstitute of Materials, School of Materials Science and Engineering, Shanghai University, 149 Yanchang Road, Shanghai 200072, ChinaInstitute of Materials, School of Materials Science and Engineering, Shanghai University, 149 Yanchang Road, Shanghai 200072, ChinaInstitute of Materials, School of Materials Science and Engineering, Shanghai University, 149 Yanchang Road, Shanghai 200072, ChinaThe development of bipolar plate materials with enhanced corrosion resistance and surface conductivity is critical for the commercial application of proton exchange membrane fuel cells (PEMFCs). The corrosion behavior and surface conductivity of electrochemically nitrided 446 stainless steel with and without the pretreatment of Cr-enrichment were investigated in the simulated PEMFC anode and cathode environments (i.e., 0.5 mol L<sup>−1</sup> H<sub>2</sub>SO<sub>4</sub> + 2 ppm HF solution bubbled with hydrogen or air at 80 °C) using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma–mass spectrometry (ICP-MS), and electrochemical measurement techniques. Extending the nitriding time from 5 to 30 min enhances the surface conductivity but reduces the corrosion resistance. After the pretreatment and 30 min of nitridation, a thin film formed on the specimen surface, which mainly consists of Cr-nitrides and -oxides with atomic fractions of 0.42 and 0.37, respectively. The Cr-enriched and nitrided specimen shows spontaneous passivation in both the simulated cathode and anode environments and higher corrosion potentials, lower passive current densities, and larger polarization resistances in comparison with the directly nitrided specimens. Its stable current densities are about 0.26 and −0.39 μA cm<sup>−2</sup> after 5 h of polarization tests at 0.6 V<sub>SCE</sub> in the cathode environment and at −0.1 V<sub>SCE</sub> in the anode environment, respectively. Its contact resistance is about 5.0 mΩ cm<sup>2</sup> under 1.4 MPa, which is close to that of the specimen directly nitrided for 120 min and slightly decreases after the potentiostatic polarization tests. These results indicate that Cr-rich pretreatment improves not only the corrosion resistance and surface conductivity of nitrided specimens but also the efficiency of electrochemical nitridation.https://www.mdpi.com/2075-4701/15/5/566Cr-rich pretreatmentelectrochemical nitridationcorrosioninterfacial contact resistancestainless steel bipolar plate |
| spellingShingle | Ronghai Xu Yangyue Zhu Ruigang Zhu Moucheng Li Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates Metals Cr-rich pretreatment electrochemical nitridation corrosion interfacial contact resistance stainless steel bipolar plate |
| title | Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates |
| title_full | Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates |
| title_fullStr | Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates |
| title_full_unstemmed | Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates |
| title_short | Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates |
| title_sort | corrosion resistance and surface conductivity of 446 stainless steel with electrochemical cr enrichment and nitridation for proton exchange membrane fuel cell pemfc bipolar plates |
| topic | Cr-rich pretreatment electrochemical nitridation corrosion interfacial contact resistance stainless steel bipolar plate |
| url | https://www.mdpi.com/2075-4701/15/5/566 |
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