The study of surface modification 304 stainless steel in simulated PEMFC environments

In order to increase the corrosion resistant and reduce the interfacial contact resistance of the stainless steel, the duplex treatment technology of electroplating Cr and plasma-assisted nitriding process for AISI 304SS is exploited. X-ray diffraction (XRD), scanning electron microscopy (SEM) and the electrochemical tests such as potentiodynamic and potentiostatic polarization in the simulation PEMFC environments are measured. XRD showed that the surface layer of the 540 degrees C and 550 degrees C were Cr and Cr2N; the 580 degrees C was the CrN and Cr2N. The nitride sample of the 550 degrees C could see the closure process of the mesh crack. Compared with the simulated PEMFC anode environment, higher corrosion resistance was showed in the simulated PEMFC cathode environment. The current density of the 540 degrees C, 550 degrees C and 580 degrees C samples were negative at the operating potential -0.1V, which would provide cathodic protection to the metallic bipolar plates. In the simulated cathode environment, the current densities of the three samples were quickly stabilized, the surface quickly formed a stable passive film.