On The Stability of Passive Film for Al-Rich Multicomponent Bulk Metallic Glass Under Long-Term Immersion in Chloride Containing Solution

Abstract

In this paper, the electrochemical characteristics and passive film stability of an Al86Ni6Y4.5Co2La1.5 bulk metallic glass were systematically investigated in a chloride containing solution by the combination of electrochemical impedance spectroscopy and high-resolution transmission electron microscopy observations. The results demonstrated that the evolution of corrosion could be divided into five distinct zones: film growth in the initial immersion; a complete passive film with a dynamic and stable process; the occurrence of pitting on the passive film; accumulation of corrosion products and the formation of continuous channels to failure. Interestingly, it was noted that in the second zone, the passive film achieved the highest stability at the middle of immersion due to the synergistic effect of film doping and thickening induced by the alloying of Y/La and Ni/Co. Afterwards, a gradual degradation of the passive film was observed, which was associated with the partial devitrification of the Y2O3 and La2O3 amorphous passive film. Correspondingly, the film/metal matrix interface underwent a transition from a flat interface to a curved one during the immersion, inducing the failure of the passive film. Our findings provide guidance for the design of Al-based amorphous alloys with high corrosion resistance.