Composite coatings with in situ formation for Fe-Ni-Cr alloy as bipolar plate of PEMFC

Fe-Ni-Cr alloy is a potential material as the bipolar plate for proton exchange membrane fuel cell (PEMFC). However, its interfacial contact resistance is too high and the corrosion resistance is too low to survive in the hostile environment. A novel approach of preparing the composite coating layers by in situ method is reported in this manuscript. The plate is first treated in acid solution, and then is heat treated at low temperature, at last is treated by electrochemical method. The ICR for the treated plate is lower than 10 mΩ cm2, and corrosion current density is less than 5 × 10−8 A cm−2. Microstructures for differential treatments have been analyzed by FE-SEM, XRD, XPS and AES as well as EPMA. The results indicate that high carbon concentration within surface area has been aroused by solution treatment, and then the conductive Cr7C3 layer has been in situ formed by heat treatment. Thereafter electro-chemical treatment has the function of clearing the surface and forming dense Cr2O3/Fe3O4 layer again upon Cr7C3/C layer, which improves the performance of bipolar plate effectively.