Corrosion resistance of Cu-Zr-Al-Y and Zr-Cu-Ni-Al-Nb bulk metallic glasses

摘要

Electrochemical tests of amorphous Cu_(46)Zr_(42)Al_7Y_5 in comparison to amorphous Zr_(58.5)Cu_(15.6)Ni_(12.8)Al_(10.3)Nb_(2.8) (Vitl06a) were conducted by potentiodynamic polarization at room temperature in 0.001-0.1 M NaCl_(aq) (pH 8). The influence of corrosion on the surface topography was studied by X-ray diffraction and SEM. Electrochemical measurements indicate a good corrosion resistance of both bulk metallic glasses in NaCl solutions with low molarity at pH 8 due to the formation of protective oxide films. However, at high NaCl molarity the Cu-Zr-Al-Y glass shows no passive layer and is very susceptible to pitting corrosion. The mechanisms of the formation of the oxide films as well as the nucleation and growth of pitting were clarified by associating microstructural investigations with the results of electrochemical measurements.