Influence of the microstructure on the corrosion behavior of magnetron sputter-quenched amorphous metallic alloys

Abstract

Numerous amorphous metallic alloys exhibit excellent corrosion resistance in acidic and/or basic aqueous solutions, mainly due to the absence of grain boundaries and other structural defects in the homogeneous phase. However, the microstructure and surface texture of the films, and thus their corrosion behavior, strongly depend on the quenching atmosphere, presure, and other deposition parameters. In this paper, we report the microstructure and corrosion behavior of magnetron sputter deposited amorphous metallic films of (Mo60Ru40)82B18 under varying sputtering atmospheres (e.g., Ar, Ar+O2 and Ar+N2 gas mixtures). Their microstructural details and topology have been studied by scanning electron microscopy and correlated with the deposition conditions. For example, films deposited in argon pressure in excess of 5 μm or in the presence of O2 (∼2 μm) in Ar (∼5 μm) exhibit columnar growth patterns, whereas addition of N2 (∼2 μm) in Ar (∼5 μm) seems to trigger crystallization of the deposits. The deposition kinetics can be understood with the help of the growth model proposed by Thornton. The influence of the microstructure and surface texture on the corrosion behavior is also discussed.