Corrosion Resistance of Cr Coating Treated by Nitriding on Stainless Steel Bipolar Plate for Proton Exchange Membrane Fuel Cell

The liquid phase plasma electrolytic nitriding technology was used to conduct short-term nitriding treatment on 316L stainless steel bipolar plate with pure Cr coating.The morphology and composition of Cr nitrided coating were characterized by scanning electron microscope and X-ray diffraction. Its corrosion resistance was tested by electrochemical test, and the interface contact resistance (R_IC) of the coating was measured. The results showed that the surface of Cr nitrided coating presented uneven cellular structure, and the coating was amorphous structure. Compared with substrate sample, the corrosion potential of Cr nitrided coating was significantly high (about +600 mV), the corrosion current density was two orders of magnitude lower than that of stainless steel substrate, and the corrosion resistance efficiency was 99.67%. The R_IC of Cr nitrided coating was 13.7 mΩ·cm², which had good conductivity.