engleski

Corrosion resistance of aluminium-tungsten amorphous alloys in the arteficial saliva

The oral environment is very demanding for materials used in dentistry - noble metals and their alloys with their superior qualities are required in many cases. The possibility of using less-expensive bulk materials coated by a layer of material with superior properties thus seems worth exploring. Such coatings should comply with several requirements: nontoxicity of the components, reliable/firm adhesion to the substrate, mechanical hardness, thermal stability and superb corrosion resistance. The aim of this work was to investigate corrosion resistance and indirect biocompatibility of aluminum-tungsten thin films for dental (medical) application, in the artificial saliva solution, at pH = 5.1, in order to establish their suitability for use in the oral environment. The results were compared with the properties of pure polycrystalline aluminum and tungsten metals in the same solution, as well as some other standard dental alloys. Corresponding results on microhardness, thermal stability, and corrosion resistance in 1 M HCl of amorphous Al-W films are presented elsewhere. Thin films of Al-W alloys were prepared by the magnetron sputtering co-deposition technique. Completely amorphous films were obtained in the 80Al20W - 67Al33W composition range. The microhardness of the amorphous films was in the range 7.5 +/- 1 GPa, larger than that of pure tungsten. Their corrosion resistance in the artificial saliva solution at pH = 5.1 were investigated using rapid corrosion tests based on the electrochemical methods: cyclic voltammetry, linear polarization, and impedance spectroscopy. The corrosion stability increased with increasing tungsten content in the alloy. The resistance of the protective surface oxide films was in the range of 10^5-10^6 Ohms cm^2, and the breakdown potential of these films shifted towards more positive potential values in the order 67Al33W, 75Al25W, 80Al20W, Al. It is concluded that aluminum-tungsten alloys are new promising materials for use in dental application.

Al-W amorphous alloys; dental materials; corrosion resistance; cyclic voltammetry; linear polarization; impedance spectroscopy

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