Abstract
Corrosion resistance and electrical conductivity of stainless steel bipolar plate remains a big challenge while it has been regarded as the most promising candidate for proton exchange membrane fuel cell. The purpose of this paper is to study the effects of pickling and passivation by sulfuric acid and a mixture of nitric and fluoric acids, respectively, on corrosion resistance and electrical conductivity of stainless steel 316L (SS316L) bipolar plate. First, pickling of the specimens of SS316L is performed in a 15 wt.% H2SO4. Afterwards, the specimens are passivated in a mixture of 12 wt.% HF and 4 wt.% HNO3. Electrochemical and interfacial conductivity tests are conducted to examine the change in corrosion resistance and electrical conductivity of SS316L. Finally, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) reveal the evolution of surface morphology, chemical composition and surface conductivity. The results show that the corrosion resistance and electrical conductivity of SS316L could be improved significantly by pickling and passivation. The increase in Cr:Fe ratio as well as a more uniform surface with higher conductivity is the main reason for the improvement of corrosion resistance and interfacial conductivity of SS316L.
Highlights
The proton exchange membrane fuel cell (PEMFC) has been considered to be a promising energy conservation device due to its high efficiency, high power density, low operating temperature, low noise, quick start-up and zero pollutions [1]
It can be seen that the corrosion potential (Ecorr.) and corrosion current density (Icorr.) of pickling and passivation treated stainless steel 316L (SS316L) was close to that of the original SS316L (Figure 1a)
The results indicate that the corrosion resistance of SS316L can be improved by pickling and passivation method described in the present paper
Summary
The proton exchange membrane fuel cell (PEMFC) has been considered to be a promising energy conservation device due to its high efficiency, high power density, low operating temperature, low noise, quick start-up and zero pollutions [1]. As a key component in PEMFC, bipolar plates account for 20–30 and 60–80% of the cost and weight, respectively [2]. Among the materials investigated for bipolar plates, stainless steel (SS) is regarded as one of the most promising candidates for PEMFC, especially in automotive applications because of its high electrical and thermal conductivity, low gas permeability, high strength and toughness, superior formability and relatively low cost [3]. A light weight of PEMFC can be achieved by utilizing ultrathin stainless steel bipolar plate with a thickness of 0.1 mm or even thinner. Corrosion of stainless steel bipolar plate remains a big challenge [4]. The improvement of corrosion resistance and electrical conductivity of stainless steel bipolar plate is of great significance for PEMFC with higher performance and longer durability
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