Transient Potential Induced Anodic Dissolution of 316L Stainless Steel in Sulfuric Acid Solution

Abstract

© The Author(s) 2019. Transient potentials, originating from the dynamic loading during the operation of proton exchange membrane fuel cells (PEMFCs), could induce severe corrosion of metallic bipolar plates under the aggressive working conditions of PEMFCs. In this study, square wave potential pulses, with the upper potential limit of 0.7 V vs. Ag/AgCl and the pulse potential limits from 0.6 to 0.3 V, are applied to 316L stainless steel (316L SS) in 5 mM H2SO4 + 2 ppm NaF at 70°C to simulate the potential variations. Results show that transient potentials enhance the anodic dissolution of 316L SS. A more negative pulse potential generates a much higher frequency of passive film breakdown events than that generated by a more positive pulse potential during the cyclic pulse tests. Analysis of the electronic properties of the passive films suggests that the disorder degree of the passive film formed at different pulse potentials is strongly associated with these breakdown events; a protective passive film with less localized states is beneficial to mitigate the dissolution induced by the transient potentials. The development of bipolar plates with less defective surface structure and assessment of its performance under transient potentials are necessary for improving PEMFC durability.