# Effectiveness of Nanotechnology Treatments in Composite Aircraft Applications
## 3 Corrosion and Fatigue Test
### Prolonged Immersion Corrosive Test  
This type of test involves a continuous and prolonged (20 days) immersion test in a solution of sodium chloride in deionized water with a concentration of 35 g/L with a variation of 1 g/L.  
According to the standard, it is necessary that each test sample has at least one duplicate within the same immersion bath; for this reason, it was decided to create three specimens for each type of sample to be tested: three raw aluminum specimens (2024 T3), three aluminum specimens with primer without nanotechnology coating, and three specimens without primer with nanotechnology coating. During the entire immersion period, once a day, the temperature of the environment (mean value: 15 \({}^{\circ}\)C) and that of the solution (mean value: 17 \({}^{\circ}\)C) were measured in each tank together with the air humidity (around  
\begin{table}
\begin{tabular}{c c} \hline  & **[mm]** \\ \hline G—gauge length & 50 \\ W—width & 12.5 \\ T—thickness & 3 \\ R—radius of fillet & 12.5 \\ L—overall length & 200 \\ A—length of reduced parallel section & 57 \\ B—length of grip section & 50 \\ C—width of grip section & 20 \\ d—central-hole diameter & 2 \\ D—end-end-hole diameter & 5 \\ \hline \end{tabular}
\end{table}
Table 1: Modified standard specimen.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Name** & **Corrosion** & **Mat-Type** & **Fatigue Load Type** & \(F_{max}\) [kN] & \(F_{min}\) [kN] & \(f\) [Hz] \\ \hline MF000 & No & Al-Raw & 1 & 11 & 0 & 5 \\ MCF001 & Yes & Al-Raw & 1 & 11 & 0 & 5 \\ MCF002 & Yes & Al-Raw & 2 & 9 & 0 & 5 \\ MCF003 & Yes & Al-Raw & 3 & 6 & 0 & 5 \\ MCF004 & Yes & Al-Primer & 1 & 11 & 0 & 5 \\ MCF005 & Yes & Al-Primer & 2 & 9 & 0 & 5 \\ MCF006 & Yes & Al-Primer & 3 & 6 & 0 & 5 \\ MCF007 & Yes & Al-Nanotech & 1 & 11 & 0 & 5 \\ MCF008 & Yes & Al-Nanotech & 2 & 9 & 0 & 5 \\ MCF009 & Yes & Al-Nanotech & 3 & 6 & 0 & 5 \\ MCS010 & No & Al-Nanotech & 1 & 11 & 0 & 5 \\ MCS011 & No & Al-Nanotech & 2 & 9 & 0 & 5 \\ MCS012 & No & Al-Nanotech & 3 & 6 & 0 & 5 \\ \hline \end{tabular}
\end{table}
Table 2: List of specimens under corrosion and fatigue tests.  
70%). Two measurements of the pH of the solutions of the three tanks were also performed, one in the middle of the test after about 10 days of immersion and one at the end to verify the constancy of the value.  
In the three tanks, it was possible to observe some important characteristics: all three tanks showed an accumulation of sodium chloride at the bottom in correspondence to each sample, as if each one had attracted the salt to itself, which had no way of adhering completely to the metal surface, precipitating into the solution. It should be noted that the solute accumulations were more consistent in the untreated raw aluminum specimens and in the nanotechnology-treated ones, while on those treated with the primer, there were no traces of salt evidence, but they could already show bubbles of the surface treatment.  
In image (A) of Figure 3, it is possible to observe the aluminum specimens marked with the identification code, before immersion in the bath and in (B) immediately after the phase of extraction from the corrosive bath. A loss of luster was noted for the raw aluminum specimens, a darker coloring and the presence of numerous encrustations of salt as well as a lower smoothness to the touch. A loss of luster was noted for the Al-primer together with surface bubble formation as previously mentioned. Finally, for the specimens treated with nanotechnologies, a loss of luster of the metal and a darker coloration were noted but with less formation of salt encrustations. Also in that case, a reduction in smoothness was found.