MICROBIALLY DEPOSITED MANGANESE AND IRON OXIDES ON PASSIVE METALS - THEIR CHEMISTRY, DISTRIBUTION, AND CONSEQUENCES FOR MATERIAL PERFORMANCE

摘要

316L stainless steel and Ti-6Al-4V corrosion coupons exposed to fresh river water ennobled the open circuit potential (OCP) to values of +365 mV_(SCE) and +400 mV_(SCE), respectively. ToF-SIMS spectra indicated that the biominerals on the metal surfaces are a mixture of Fe_2O_3, Mn_3O_4, and MnOOH on fully ennobled coupons, while a mixture of Fe_3O_4, Fe_2O_3, Mn_3O_4, and Mn_2O_3 on partially ennobled coupons. Biomineralized manganese and iron oxides on the 316L stainless steel surfaces, regardless of the oxidation states, endanger the material integrity in a similar manner, as evidenced by the elevated OCP and increased cathodic current density upon mild polarization.