XPS Study of the Surface Oxide Film Formed on Al87Fe10Nb3 Melt Spun Amorphous Alloys

A. GUTIERREZ; F. AUDEBERT; A. GARCÍA ESCORIAL

Sevilla

Congreso; 8º European Conference on Applications of Surface and Interface Analysis; 1999

Amorphous alloys are technologically important due to their improved mechanical properties and their good corrosion resistance. The alloy composition is a fundamental factor in determining its amorphous or crystalline character. Also the processing method, which usually involves rapid solidification techniques, is a critical factor. The corrosion properties of amorphous alloys are influenced by the properties of the passive layer formed by interaction with the atmosphere during cooling. In the present work we present an XPS study of the passive layer of Al87Fe10Nb3 melt-spun amorphous alloy at both the internal side (that cooled in contact with the wheel) and the external side (that cooled in contact with air). The passive layer is composed of aluminium hydroxides, with an approximate thickness of 30 AA at both sides. The external side of the ribbon presents a second region below this passive layer, with some remanent hydroxides content extending over a thickness of about 130 AA. This second region is absent at the internal side, probably due to a faster solidification and a less direct interaction with air. Water adsorption is observed at the external side up to a depth of 100 AA, suggesting certain degree of porosity. Passive layer formation seems to occur by oxidation during cooling, followed by water adsorption and hydroxides formation. The higher porosity of the external side of the ribbon leads to the formation of the second region with remanent presence of hydroxides and water.