Approach to Enhancement Mechanism of Resistance to Corrosion of Weathering Steels by Artificially Synthesized Rusts

摘要

Colloidal particles of alpha-, beta, gamma-FeOOH, Fe_3O_4 and poorly crystallized iron oxide, the components of steel rusts, were prepared by hydrolysis and oxidation of aqueous solutions of Fe(II) or Fe(III) containing Ti (IV), Cr (III), Cu (II) and Ni (II) which enhance resistance to corrosion. The obtained rust particles were characterized by ICP, TEM, XRD, EXAFS, Mossbauer spectroscopy and measurement of specific surface area. Except for several cases the addition of these metal ions reduced the crystallinity and particle size of the rusts. The decrease in particle size of beta-FeOOH rust by Ti (IV) addition and the reduction of crystallinity of alpha-FeOOH rust by Cu (II) addition were especially marked. The influences of metal ions depended on the kinds of metal ions and rusts. No metal ion effectively reducing particle sizes over all the rusts was found out in the metal ions under investigation. These results suggest that suitable alloying elements should be selected based on the corrosion environment and multiple addition of the alloying elements is required to form dense rust layer.