Corrosion protection of AA7449-T7951 friction stir welds by laser surface melting with an Excimer laser

The corrosion protection afforded by laser surface melting (LSM) AA7449-T7951 friction stir welds was investigated. LSM produced melting of the constituent particles and formation of a homogeneous 3–5 μm thick layer. Electrochemical tests showed a reduction in cathodic reactivity after LSM. The breakdown potentials, however, did not change significantly, indicating an anodically reactive surface. In situ and ex situ observation after immersion in 0.1 M NaCl showed that LSM reduced the depth attack in the weld region (particularly the HAZ), affording sacrificial protection to the substrate. Delamination of the treatment can occur during corrosion propagation.

► Friction stir welds in AA7449-T7951 are susceptible to corrosion in the heat-affected zone. ► Surface treatment with an Excimer laser improves the weld corrosion resistance. ► The homogeneous laser-treated surface layer offers sacrificial protection. ► In situ X-ray microtomography indicated a risk of delamination of the laser-treated layer.