## 2 Materials and Methods
### Electrolytic Zinc Coating Process  
Electolytic zinc plating was carried out under laboratory conditions in a commercial electroplating facility. Given the geometry of the test samples, a rack plating method was employed to ensure uniform deposition. The deposition process was conducted in a cyanide-free alkaline electrolyte bath, primarily consisting of an aqueous solution of Na\({}_{2}\)[Zn(OH)\({}_{4}\)], with a Zn\({}^{2+}\) concentration of 15 \(\pm\) 1 g\(\cdot\)L\({}^{-1}\) at a temperature of 25 \(\pm\) 1 \({}^{\circ}\)C. To maintain a stable pH range of 13.8-14.0, NaOH (160-170 g\(\cdot\)L\({}^{-1}\)) was added to the bath. Additionally, sulphites and gluconates were incorporated to enhance electrolyte conductivity and promote uniform coating deposition [24]. The current density was set at 1.0 A\(\cdot\)dm\({}^{-2}\), and the zinc anode used in the process had a declared purity of 99.99%. To statistically evaluate the relationship between coating mass increase and plating duration, five deposition time intervals were selected:  
* 900 s (15 min)
* 1800 s (30 min)
* 2700 s (45 min)
* 3600 s (60 min)
* 4500 s (75 min)  
A detailed breakdown of the electrolytic plating procedure is provided in Table 3.  
Given the planar dimensions of the test samples (160 \(\times\) 65 mm), the total coated surface area was calculated as 0.0208 m\({}^{2}\) (0.160 \(\times\) 0.065 \(\times\) 2), excluding the suspension hole and sheared edges. Accordingly, 1 m\({}^{2}\) of zinc coating was sufficient to cover approximately 48.1 steel samples on both sides (0.0208\({}^{-1}\)). This factor was incorporated into the calculation of the surface mass of deposited zinc (\(m_{Zn}\), g\(\cdot\)m\({}^{-2}\)), determined as the difference between  
\begin{table}
\begin{tabular}{c c} \hline
**Scheme** & **Brief Description of the Operation** \\ \hline
1 &
\begin{tabular}{c} Degreasing in an 8\% NaOH solution \\ (immersion time: 480 s, temperature: 60 \(\pm\) 2 \({}^{\circ}\)C) \\ \end{tabular} \\ \hline
2 &
\begin{tabular}{c} Rinsing (2\(\times\)) in demineralized water \\ (immersion time: 30 s per rine, temperature: 21 \(\pm\) 1 \({}^{\circ}\)C) \\ \end{tabular} \\ \hline
3 &
\begin{tabular}{c} Electrolytic degreasing in a 5\% NaOH solution \\ (immersion time: 240 s, temperature: 60 \(\pm\) 2 \({}^{\circ}\)C) \\ \end{tabular} \\ \hline
4 &
\begin{tabular}{c} Rinsing (2\(\times\)) in demineralized water \\ (immersion time: 30 s per rine, temperature: 21 \(\pm\) 1 \({}^{\circ}\)C) \\ \end{tabular} \\ \hline
5 &
\begin{tabular}{c} Pickling (acid cleaning) in a 10\% HCl solution \\ (immersion time: 120 s, temperature: 25 \(\pm\) 1 \({}^{\circ}\)C) \\ \end{tabular} \\ \hline
6 &
\begin{tabular}{c} Rinsing (2\(\times\)) in demineralized water \\ (immersion time: 30 s per rine, temperature: 21 \(\pm\) 1 \({}^{\circ}\)C) \\ \end{tabular} \\ \hline
7 &
\begin{tabular}{c} Electrolytic zinc deposition (as described above) \\ \end{tabular} \\ \hline
8 &
\begin{tabular}{c} Rinsing (3\(\times\)) in demineralized water \\ (immersion time: 30 s per rine, temperature: 21 \(\pm\) 1 \({}^{\circ}\)C) \\ \end{tabular} \\ \hline
9 &
\begin{tabular}{c} Drying of samples in a continuous dryer \\ (drying time: 720 s, temperature: 60 \(\pm\) 5 \({}^{\circ}\)C) \\ \end{tabular} \\ \hline
10 & Final visual inspection \\ \hline \end{tabular}
\end{table}
Table 3: Electrolytic zinc plating process.  
the mass of a single steel substrate sample before (\(m_{S}\)) and after coating (\(m_{S+Zn}\)). The constant 48.1 m\({}^{-2}\) was applied to scale the deposited zinc mass to 1 m\({}^{2}\) of surface area:  
\[m_{Zn}=(m_{S+Zn}-m_{S})\cdot\)48.1 \(\left(g\cdot m^{-2}\right) \tag{2}\]