Real-time monitoring of the uniform corrosion rate of aluminum using picosecond acoustic method

Abstract

This paper introduces a novel operando measurement technique to monitor the degradation rate of aluminum (a thin layer of Al deposited on a sapphire substrate), first in a commercial aluminum etching solution, and then in a sodium chloride solution using a pump–probe spectroscopy technique. By measuring picosecond acoustic signals, the instantaneous dissolution of an Al thin layer can be monitored with nanoscale resolution along the z-axis, corresponding to the thickness of the material. In contrast, the resolution in the x and y directions, which lie in the plane of the material, operates at a micrometer scale. This distinction highlights the high sensitivity of the technique for precise tracking of dynamic processes. This new type of real-time measurement provides insights into the early stages of the Al corrosion process, with high sensitivity, and illustrates the potential of this technique for the study of the rupture of passive films.