## 3 Results and Discussion
### Characterization of Corrosion Products after 28 Days of Immersion in a 5% NaCl Solution  
#### 3.3.1 SEM of Corrosion Products  
The surface morphology of the corrosion products after 28 d of immersion in a 5% NaCl solution is shown in Figure 7. The globular Cu particles observed in Figure 7a suggest the formation of copper oxides or chlorides because the solution became blue-green. This assumption was confirmed with the EDS and XRD analyses of the corrosion products. The \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Coatings**} & **Weight of Samples** & **Weight of Samples** & **Amount of Water Permeated (g) = Weight** & \multirow{2}{*}{**Permeability**} \\  & **before Water** & **after Immersion in** & **of Samples after Water** & \\  & **Immersion (g)** & **Water (g)** & **Immersion–Weight of Samples before** & **Ratio** \\ \hline Concrete & 802.3 & 825.2 & 22.9 & - \\ \hline Cu & 785.2 & 798.0 & 12.8 & 0.56 \\ \hline Ti & 885.1 & 896.7 & 11.6 & 0.50 \\ \hline
85 Zn-15 Al & 815.4 & 827.8 & 12.4 & 0.54 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Water permeability measurement. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Sample ID**} & **4 Weeks** & **8 Weeks** \\ \hline Ti & 9.2 mm & 12.5 mm \\ \hline
85 Zn-15 Al & 13.3 mm & 21.2 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._details are described in subsequent sections. In addition to the globular shape, the concrete surface revealed coating delamination. This result was in good agreement with the digital images shown in Figure 6a, which illustrates the concrete surface and some Cu particles. In comparison, the Ti corrosion products were homogenous and uniformly covered the surface with fine particles (Figure 7b), which filled the remaining pores, as observed after the deposition of the coating (Figure 3b). The corrosion products formed on the 85 Zn-15 Al coating exhibited filamentous, globular, and flake-like morphologies (Figure 7c). The globular and flake-shaped morphologies might be attributed to the formation of simonkolleite (Zn\({}_{5}\)(OH)\({}_{8}\)Cl\({}_{2}\)), while a needle structure reveals active Zn particles in the coating [31, 43, 44]. As the corrosion products were also defective, the ingress of aggressive ions, that is, Cl\({}^{-}\) and CO\({}_{3}\)\({}^{2-}\) ions from the atmosphere, is also possible. Therefore, the 85 Zn-15 Al coating exhibited the highest penetration depth of CO\({}_{2}\) after eight weeks of exposure (Table 3). The EDS analysis results of the corrosion products are listed in Table 5. The amount of Cu in the corrosion products decreased by more than twice (Table 5) that in the coating (Table 1). This result suggests that Cu was delaminated from the concrete surface; therefore, a slight amount, that is, 1.24% Ca, was observed (Table 5). This result was corroborated by the images obtained after immersion in the NaCl solution (Figure 6). The high amounts of Na and Cl revealed the deposition of NaCl, which led to the formation of copper chloride as a corrosion product (this was confirmed by XRD, as indicated in the subsequent paragraph). However, the amount of O remained identical to that observed after the coating application. This means no oxidation occurred in the coating after immersion in the NaCl solution for 28 days, in contrast to delamination and dissolution. Ti corrosion products exhibited  
Figure 7: SEM of corrosion products formed on (**a**) Cu, (**b**) Ti, and (**c**) 85 Zn-15 Al coatings after 28 days of immersion in 5 wt.% NaCl solution. a slight reduction in their total content compared with that of the coating. Na and Cl were in nominal amounts, suggesting the averting nature of Ti or its oxide to interact with NaCl. In the case of the 85 Zn-15 Al corrosion products, the amount of Zn was reduced by almost twice the amount of the coating, revealing the deterioration of Zn compared with Al, which is attributed to the galvanically active nature of Zn.