Corrosion behaviour of laser-cleaned AA7024 aluminium alloy

摘要

Graphical AbstractLaser-cleaned surface of hot-rolled AA7024-T4 alloy exhibited higher corrosion resistance in 3.5 wt.% NaCl solution than the as-received, due to the removal of the original less protective oxide layer consisting of MgO and MgAl2O4and formation of more protective oxide layer containing Al2O3and MgO.Display OmittedHighlights•Laser cleaning removed the original oxide layer comprising of MgO+MgAl2O4.•Laser cleaning induced a formation of oxide layer consisting of Al2O3+MgO.•Laser-cleaned surface exhibited higher corrosion resistance than the as-received.•Newly formed oxide film by laser cleaning offered better protection against corrosion.AbstractLaser cleaning has been considered as a promising technique for the preparation of aluminium alloy surfaces prior to joining and welding and has been practically used in the automotive industry. The process is based on laser ablation to remove surface contaminations and aluminium oxides. However the change of surface chemistry and oxide status may affect corrosion behaviour of aluminium alloys. Until now, no work has been reported on the corrosion characteristics of laser cleaned metallic surfaces. In this study, we investigated the corrosion behaviour of laser-cleaned AA7024-T4 aluminium alloy using potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The results showed that the laser-cleaned surface exhibited higher corrosion resistance in 3.5 wt.% NaCl solution than as-received hot-rolled alloy, with significant increase in impedance and decrease in capacitance, while SVET revealed that the active anodic points appeared on the as-received surface were not presented on the laser-cleaned surfaces. Such corrosion behaviours were correlated to the change of surface oxide status measured by glow discharge optical emission spectrometry (GDOES) and X-ray photoelectron spectroscopy (XPS). It was suggested that the removal of the original less protective oxide layer consisting of MgO and MgAl2O4on the as-received surfaces and the newly formed more protective oxide layer containing mainly Al2O3and MgO by laser cleaning were responsible for the improvement of the corrosion performance.