**1. Introduction**

Friction stir welding (FSW) is a recent solid-state joining technique developed by the Welding Institute [1,2]. This technique has promising applications on difficult-to-weld alloys, i.e., age-hardening aluminum alloys [3,4]. FSW technique has been successfully applied to Al-Cu 2XXX series [5,6], Al-Si-Mg 6XXX [7,8], and Al-Zn-Mg 7XXX series alloys [9,10].

The 7XXX series aluminum alloys are widely used in aircraft and automotive industry due to the high tensile strength on weight ratio. The corrosion resistance of the alloy is significantly affected by the presence of Zn and Mg, which could induce several corrosion phenomena, such as localized corrosion such as pitting [11–13], intergranular [14,15], and stress-corrosion cracking [16,17].

The corrosion behavior of such alloys is strictly related to the temper. Several authors confirm that the 7XXX alloy exhibits SCC susceptibility in peak-aged conditions (T6 temper). However, over-aging (T7) or retrogression and re-aging (RRA) treatments are not critical compared to SCC [18,19]. Even if FSW is a solid-state joining technique, it is well known that it implies deep modifications to the alloy's microstructure and precipitates' distribution in the welding zones [20–23]. Therefore, this process can significantly affect the corrosion resistance and SCC [24,25].

The aim of this work is the study of the SCC susceptibility of AA 7075 T6 FSW butt joints by means of constant deformation tests with a four-point bending device (4PBD), uniaxial constant loading (CL) and slow strain-rate (SSR) tests in NaCl 35g/L aerated solutions at room temperature. During the tests, the open circuit potential (OCP) was monitored. The corrosion morphology was observed after exposure by means of the optical microscope and the scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy device (EDX).

#### **2. Materials and Methods**
