PASSIVE FILM CHEMISTRY on 316L STAINLESS STEEL ENNOBLED BY BIOMINERALIZED MANGANESE

摘要

The effect of ennoblement on chemistry of passive films on 316L stainless steel (SS) wasrnquantified using surface-sensitive analytical techniques. Under well-defined laboratory conditions, SSrncoupons were ennobled to ～ +350mVsCE by biofilms of manganese-oxidizing bacterium Leptothrixrndiscophora SP-6. Ennobled coupons were analyzed by x-ray photoelectron spectroscopy (XPS) andrntime-of-flight secondary ion mass spectroscopy (TofSIMS). From the XPS depth profiles of Fe, Cr, O,rnNi, C and Mn, we evaluated thickness of the passive layers before and after ennoblement, while thernTofSIMS depth profiles were used to evaluate spatial distribution of Mn, Cr, Fe and Ni on the surface.rnBecause the ennobled coupons were covered with biomineralized deposits, sputtering was used tornremove these deposits under ultrahigh vacuum (UHV) conditions before probing the chemistry of thernunderlying passive layers. The main conclusion of the paper is that oxide layers on the ennobledrncoupons are significantly thinner than those on the pre-ennobled coupons, which may, hypothetically,rncontribute to their susceptibility to localized corrosion.