Localised corrosion assessment of friction-stir welded AA7050-T76511 alloy: galvanic interactions and microstructural effects

Abstract

In this work, the localised corrosion behaviour of friction stir welded (FSW) AA7050-T76511 alloy was studied using micro-electrochemical scanning methods combined with surface characterisation. The study focused on macro galvanic interactions between the stir zone (SZ) and thermo-mechanically/heat-affected zones (TMAZ/HAZ), considering distinct initial micro-structures created by an L-bent pre-welding configuration at advancing and retreating sides. Agar-visualisation, local electrochemical impedance spectroscopy and scanning vibrating electrode technique revealed significant galvanic coupling. The TMAZ/HAZ regions behaved anodically relative to the SZ, with notably higher electrochemical activity observed at the AS. These findings demonstrate the critical influence of initial microstructural differences on corrosion susceptibility in FSW AA7050 alloys.