Corrosion Behaviors of Magnetron Sputtered NiCrCN Coating in Proton Exchange Membrane Fuel Cell Cathode Environment
Unbalanced magnetron sputtering technology was used to deposit NiCrCN coating on 316L stainless steel surface.The micromorphology and corrosion resistance in the simulated cathode environment of a proton exchange membrane fuel cell(PEMFC)(0.5 mol·L-1 H2SO4+2 mg·L-1 HF,air injection,70 ℃)of the coating prepared at different Cr target currents were studied.The results show that the prepared NiCrCN coatings were composed of metal nickel,CrN,Cr2 N,Cr7 C3 phases.The surface of the coating prepared at 4 A Cr target current was smooth and compact,while the columnar crystal structure of the coatings prepared at 2,6 A Cr target currents was obvious.After polarization at constant potential of 0.6 V and cyclic polarization at high potential of 1.0 V in the simulated cathode environment of PEMFC,the corrosion current density of the coating first decreased and then increased with the increase of Cr target current.The corrosion current density of the coating prepared at 4 A Cr target current was the smallest,and the constant potential polarization curve was more stable;the mass concentration of metal ions dissolved in corrosion solution in constant potential polarization was the smallest,and the surface corrosion degree was the lightest.The charge transfer resistance of the coating prepared at 4 A Cr target current after immersion for 14 d was 1 order of magnitude higher than that of 316L stainless steel.The best NiCrCN coating for PEMFC service under normal operation,quick start-up/shut-down and long-term rest conditions was the coating prepared at 4 A Cr target current.
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