## 3 Results and Discussion
Figure 4(a) illustrates the zinc deposition on the surfaces of pure aluminum and the 6061 aluminum alloy via electrodeposition. It can be seen that the zinc grains on the pure aluminum (Figure 4(a)) are larger than those of the 6061 aluminum alloy (Figure 4(b)). Furthermore, there is a tendency for zinc grains in pure aluminum to undergo agglomeration. Figure 6 presents the cross-sectional views of the zinc coatings on anodes made from pure aluminum (Figure 5(a)) and aluminum alloy 6061 (Figure 5(b)), with average thicknesses measured at 20.0 \(\upmu\)m and 17.8 \(\upmu\)m, respectively. Zinc and its oxide, being the predominant coating materials, exhibit distinct demarcations between the zinc layer and the aluminum substrate, as evidenced by the SEM images and the EDX mapping. The electrodeposition process, which utilizes only an aqueous zinc sulfate solution, leads to the formation of a thick layer of zinc with large grains, which can be attributable to the high rate of deposition. To moderate this deposition rate, we introduced EDTA as a chelating agent into the solution. The presence of EDTA results in the formation of Zn chelates, effectively slowing the rate of zinc deposition. Figure 4: SEM images and EDX mapping at the surface of the zinc-coated anode—(**a**) pure aluminum and (**b**) aluminum alloy 6061—using aqueous zinc solution during electrodeposition. EDTA as the complexing agent will bind with the metal ion and influence its reactivity and mobility in the electrolyte. It leads to more control and uniformity of the quality of the coating, including better coating-substrate bonding, a denser layer, and improved uniformity on a complex-shaped substrate. Meanwhile, citrate based only within the electrolyte is mostly used to reduce its original compound to a metal ion [36; 37]. In an aqueous electrolyte, zinc ions can form various complexes, including Zn(H\({}_{2}\)O)\({}_{6}^{2+}\). The presence of complexing agents such as citrates or EDTA will influence the formation of these complexes and subsequently affect the deposition process. The structures of the EDTA complexes and the disodium salt of EDTA are illustrated in [38]. In the presence of complexing agents, zinc ions form stable complexes such as Zn(EDTA)\({}^{2-}\) or Zn(Citrate) complexes. The complexation reduces the concentration of free zinc ions, moderating the deposition rate and resulting in a finer and more uniform deposit. Figure 7 presents the SEM images and EDX mapping of the surfaces of pure zinc-coated aluminum and the 6061 aluminum alloy, used as anodes, which were treated with EDTA in the aqueous zinc solution during the electrodeposition process. The SEM images reveal that the zinc coating appears as a thin film on the aluminum anodes. The surface structures of the zinc-coated aluminum anodes are comparable to those of the uncoated ones. In addition, the EDX mapping shows the presence of base aluminum and zinc elements. Figure 6: SEM images and EDX mapping at the cross-section of the zinc-coated anode—(**a**) pure aluminum and (**b**) aluminum alloy 6061—using aqueous zinc solution during electrodeposition. Figure 8 illustrates the polarization curves for pure Al, Zn-pure Al, and Zn(EDTA)-pure Al anodes. In the figure, it is apparent that the pure Al anode has the most positive corrosion potential, followed by Zn-pure Al, while Zn(EDTA)-pure Al exhibits the most negative corrosion potential, as detailed in Figure 2.0 In general, the charge transfer coefficient (\(\alpha_{a}\)) indicates that a higher value leads the interfacial potential to lower the free energy that impedes electrochemical reaction. As a result, the activation overpotential is further decreased; then, current densities are improved, and the effectiveness of the electrochemical reactions is improved [39]. Furthermore, the corrosion current density (\(I_{corr}\)) increases with the application of the zinc coating. In particular, the highest \(I_{corr}\), indicative of the best corrosion resistance, is achieved when EDTA is added during the zinc electrodeposition process.