Effect of Surface Composition on Contact Resistivity and Corrosion Resistance of 316L Stainless Steel

Abstract

In order to produce 316L stainless steel separators with low contact resistivity and low cost, an attempt was made to reduce the contact resistivity of 316L steel by acid treatment. In the present work, the contact resistivity and corrosion resistance of acid-treated 316L stainless steels were investigated. Elemental composition, thickness and structure of the passive film on the steel surface were analyzed with transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It is found that the contact resistivity of the stainless steel is closely related to the ratio of Fe in oxide-form in the passive film, irrespectively of the thickness of passive film. When the proportion of Fe in oxide-form to the sum of Fe and Cr in oxide-form, i.e. Fe_ox/(Fe_ox+Cr_ox) is lower than ca. 40 at%, the contact resistivity is reduced to lower than 10 mΩ cm². Besides, the corrosion resistance of the acid-treated stainless steel having low contact resistivity is very high. Power generation test shows that I – V characteristic and durability of the cell assembled using the acid-treated 316L steel separators of low contact resistivity are equivalent to those of the cell assembled using carbon-coated separators.