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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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-05-01
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| Series: | Metals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-4701/15/5/566 |
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| Summary: | 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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| ISSN: | 2075-4701 |