Study of the structure and the morphology of oxide films on amorphous Al-Fe-Ce a

2019-05-12 21:36:11

films CE Passive oxide XPS

责任者: Mansour, Azzam N.;Melendres, Carlos A. 单位: Naval Surface Warfare Cent, Silver Spring, MD, USA 来源出处: Journal of the Electrochemical Society,1995,142(6):1961-1968 摘要: Aluminum-based metallic glasses are of technological importance due to their high strength, low density, and anticipated high resistance to corrosion. We report on the corrosion characteristics of melt-spun ribbons of Al90Fe10-xCex (x = 3, 5, and 7). The amorphous alloys showed excellent corrosion properties in aqueous NaCl. We have also examined the composition, structure, and morphology of the native and passive oxide films using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and angle-resolved XPS. We show that the composition of the native oxide film is that of AlOx(OH)y. The thickness of the native oxide is estimated from angle-resolved XPS data to be about 1.6 to 3.1 nm (i.e., nanometer). Passive films were formed in 0.9 weight percent (0.15M) NaCl solution by potentiostating below the pitting potential for 30 and 60 min. The passive oxide films contain oxidized Al, Fe, and Ce. The chemistry of Al in the passive oxide films is also that of AlOx(OH)y. Iron appears to be present in the passive film as Fe3O4 and Fe2O3 and/or FeOOH with varying mole fractions depending on alloy composition. Cerium in the passive film appears to be present in the +3 oxidation state as Ce2O3 or Ce(OH)3. A small fraction of Ce in the passive film of Al90Fe3Ce7 is present in the +4 oxidation states as CeO2. 关键词: Aluminum alloys;Morphology;Oxides;X ray photoelectron spectroscopy;Scanning electron microscopy;Corrosion;Sodium chloride;Composition;Structure (composition);Pitting;Passivation;Cerium;Oxidation;Oxide films;Mole fraction