Mechanisms of laser cleaning induced oxidation and corrosion property changes in AA5083 aluminum alloy

Abstract

Laser cleaning of metallic alloys for the purpose of removal of metal oxide layers is based on laser thermal ablation. In laser thermal ablation, the interaction between the laser beam and oxide layer may generate significant thermal effects to induce additional thermal oxidation or even melting a thin layer of the underlying surface. The change of surface oxide status may subsequently affect corrosion behavior of the metallic alloys. In this work, the effects of laser cleaning on corrosion behavior of hot-rolled AA5083-O aluminum alloy were investigated using electrochemical impedance spectroscopy. The results showed that the laser-cleaned surfaces exhibited higher corrosion resistance in 3.5 wt. % NaCl solution than the as-received alloy, with a significant increase in impedance and reduction in capacitance. The corrosion behavior was correlated to the change of surface oxide status measured by glow discharge optical emission spectrometry, x-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. It was concluded that the laser cleaning removed the original, less protective oxide layer consisting of a discontinuous MgO/MgAl2O4 outer layer (∼20 nm) and MgO/MgAl2O4 particles dispersed inner layer (∼300 nm) on the as-received surface but resulted in the formation of more protective oxide layer containing mainly Al2O3 and MgO, which were responsible for the improvement of the corrosion performance. The laser fluence played an important role in determining the thickness of the newly formed oxide layers that subsequently affected the corrosion performance of laser-cleaned alloy.