**5. Conclusions**

The paper studied the stress-corrosion cracking behavior of AA7075 T6 aluminum joints made by FSW as a function of loading conditions. SCC tests were performed by considering constant deformation (4PBB and CL) conditions and SSR conditions in aerated NaCl 35g/L solution at room temperature.

Certain susceptibility to SCC was demonstrated for AA 7075 FSW butt joints tested in this work mainly at the TMAZ/HAZ as nucleation of crack embryos occurred during both CL and SSR tests. However, high dissolution rate of the metal inside the localized attack prevents the achievement of critical crack size to promote its propagation up to rupture.

Slight decrease in the free corrosion potential was noticed because of the modification of the microstructure introduced by the welding process mainly at the TMAZ/HAZ and the nugge<sup>t</sup> with respect the base material. As the TMAZ/HAZ zone is characterized by low tensile strength compared to both the nugge<sup>t</sup> and the base material, it is preferentially strained under loading conditions. The plastic strain then enhances the active dissolution rate of the metal matrix and severe attack takes place, thus hindering SCC crack propagation.

The penetration depth of the intergranular attack was deeper after the four-point bent-beam tests compared to all the other testing techniques. Preferential dissolution along the grain boundaries was found in heat-a ffected zones and the attack follows the elongated grain structure along the rolling direction.

**Author Contributions:** Methodology, S.L., C.T. and S.B.; Investigation; S.L., C.T. and S.B.; Data Curation, G.D. and M.C.; Writing—original draft of the paper, M.C., S.B., G.D., C.G., S.L., C.T. and T.P. Writing—Review & Editing T.P., C.G. and M.C. Supervision, T.P. and C.G.; Project Administration, T.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding

**Conflicts of Interest:** The authors declare no conflict of interest.
