Effects of Hydrogen and Stress on Anodic Dissolution of 304 Stainless Steel in Simulated Anode Environment of Polymer Electrolyte Membrane Fuel Cell

摘要

The mechano-electrochemical effects of hydrogen and tensile stress on the anodic dissolution of type 304 stainless steel in simulated anode environment of polymer electrolyte membrane fuel cell (PEMFC) are investigated by potentiodynamical polarization tests, Mott-Schotky measurements and XPS characterization. The results reveal that hydrogen charging and tensile stress promote the anodic dissolution due to the increased donor density and difiusivity coefficient of vacancy in the passive film. Hydrogen dissolved in passive film decreases the ratio of O~2/OH~- in the passive film and also decreases the thickness of the passive film layer, resulting in increased film/solution interface potential and thus enhanced anodic dissolution rate of the passive film. The effect of hydrogen on the anodic dissolution rate in the active-passive transition region, which happens to be in the anode working potential range of metal bipolar plates of PEMFC, is more obvious than that in the steady passive potential region. The synergistic effect of hydrogen and stress on anodic dissolution is higher at the intermediate hydrogen charging current densities range than that at either lower or higher current densities range. These results indicate that dissolved hydrogen and applied stress on metal bipolar plates greatly promote its anodic dissolution rate in anode environment of PEMFC.