## 3 Results and Discussions
### Wettability Behavior  
In order to assess the relationship between the different obtained morphologies and the surface wettability behavior, the water contact angles of the as-received and modified samples were measured and are shown in Figure 5 and Table 3.  
After roughening pretreatment, the aluminum alloys, ultrasonically cleaned and dried, showed static contact angles lower than 25\({}^{\circ}\) with water in accordance with [PERSON] theory. Indeed, as stated by the theory of [PERSON], the wettability of the hydrophilic surface increases when its roughness increases. The substrates after the growth of the self-assembled silane monolayer exhibited a great change in the surface states by altering their wetting properties. Figure 4: FTIR spectra of A-WS surface. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Samples** & **CA (\({}^{\circ}\))** & **SA (\({}^{\circ}\))** \\ \hline A\_R & 69 \(\pm\) 3\({}^{\circ}\) & – \\ A\_RS & 101 \(\pm\) 2\({}^{\circ}\) & 55 \(\pm\) 6\({}^{\circ}\) \\ A\_W & 16 \(\pm\) 2\({}^{\circ}\) & – \\ A\_WS & 174 \(\pm\) 3\({}^{\circ}\) & \(>\)90\({}^{\circ}\) \\ A\_N & 23 \(\pm\) 3\({}^{\circ}\) & – \\ A\_NS & 160 \(\pm\) 3\({}^{\circ}\) & 26 \(\pm\) 5\({}^{\circ}\) \\ A\_F & 12 \(\pm\) 2\({}^{\circ}\) & – \\ A\_FS & 179 \(\pm\) 3\({}^{\circ}\) & 0\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of water contact and sliding angles at AA6082 surfaces after different treatment steps. The wettability of the surfaces depends sensitively on both surface morphology and surface energy. In fact, the roughening pretreatment induced the decrease in the water contact angle of the as-received aluminum surface from 69 \(\pm\) 3\({}^{\circ}\) to \(<\)25\({}^{\circ}\). Then, these surfaces became superhydrophobic with a water contact angle higher than 150\({}^{\circ}\) after silane deposition. This rise in contact angle is a result of the reduction in the surface energy thanks to the alignment of hydrophobic organic alkyld chains on the topside of the self-assembled silane monolayer. We also evaluated the effect of silane deposition on the surface of the as-received surface. The water contact angle of the A_R surface increased from around 69\({}^{\circ}\) to around 101\({}^{\circ}\) after silanization, confirming the decrease in the surface energy. The best result was observed for the A_FS sample that is characterized by an average water CA of around 180\({}^{\circ}\) and a very low water sliding angle (\(\approx\) 0\({}^{\circ}\)). In fact, the water droplet fell down, hit the substance, and directly rebounded upward before rolling off the Al surface without any residual water. Instead, the A_NS sample showed an average WCA of about 160\({}^{\circ}\) with an intermediate WSA (26 \(\pm\) 5\({}^{\circ}\)), and the A_WS was characterized by an WCA of about 174\({}^{\circ}\) and a high water adhesion on its surface (SA \(>\) 90\({}^{\circ}\)). This difference on the water repellency behavior between the three batches is due to the transition between [PERSON] and Cassie-Baxter regimes [24]. According to [PERSON]'s model, the water fully penetrates the surface valleys [39]. Thus, it is a homogeneous wetting mode resulting in a high contact angle and high water adhesion to the surface. However, in the Cassie-Baxter model, the surface  
Figure 5: Images of water contact angles (CAs) and sliding angles (SAs) with average values and errors on Al alloys surface: (**a**) A_R; (**b**) A_W; (**c**) A_N; (**d**) A_F where a\({}_{0}\) is the just-cleaned sample, b\({}_{0}\) is the boiled sample, and c\({}_{0}\) and d\({}_{0}\) are the etched samples. roughness traps air pockets and the water rests on the air/solid interface; thus, the water droplets on the surface are easy to roll [40]. The air entrapped in the liquid/solid interface of the A_FS surface reduces the contact area between the water droplet and the sample surface, according to the Cassie-Baxter state, inducing a high water repellency at a null sliding angle.