## 3 Results and Discussion
### Characterization of Steel Reinforcement Passivation Based on Dynamic Potential Polarization Curve
By analyzing these parameters, it is possible to quantitatively evaluate the passivation status and corrosion risk of steel reinforcements in concrete structures. This information can guide engineers and researchers in developing appropriate strategies to mitigate corrosion-related issues and ensure the long-term durability of concrete structures. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Passivation** & **b\({}_{1}\)** & **b\({}_{2}\)** & **B** & **i\({}_{\text{corr}}\)** \\
**Time (d)** & **(mV/Decade)** & **(mV/Decade)** & **(mV/Decade)** & **(\(\mu\)A/cm\({}^{2}\))** & **E\({}_{\text{corr}}\) (V)** \\ \hline
0 & 512.86 & 128.59 & 44.64 & 0.6292 & \(-\)0.2853 \\
1 & 562.29 & 111.16 & 40.30 & 0.1513 & \(-\)0.2566 \\
2 & 316.25 & 105.66 & 34.39 & 0.0596 & \(-\)0.2535 \\
3 & 267.34 & 98.49 & 31.25 & 0.0420 & \(-\)0.2394 \\
4 & 326.57 & 109.95 & 35.72 & 0.0382 & \(-\)0.1974 \\
5 & 249.58 & 107.09 & 32.54 & 0.0276 & 0.1872 \\
6 & 289.43 & 108.56 & 34.28 & 0.0338 & \(-\)0.1883 \\
7 & 181.52 & 88.40 & 25.81 & 0.0237 & \(-\)0.1867 \\
10 & 144.63 & 78.69 & 22.13 & 0.0185 & \(-\)0.1708 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The Tafel curve parameters of steel reinforcement passivation. Figure 7: The dynamic potential polarization curve during the passivation process of steel reinforcements in concrete. Table 2 shows that as the soaking test time increases, the anode Tafel slope (b\({}_{1}\)) significantly decreases. This indicates that the oxide film on the carbon steel working electrode gradually forms and tends to stabilize, which is consistent with the results in the previous study [34]. The corrosion potential (E\({}_{\text{corr}}\)) increases and is much higher than \(-0.275\) V, indicating that the passivation film on the surface of the steel reinforcement electrode is forming and maintaining stability. When the passivation film stabilizes, the anode reaction activity of the steel working electrode significantly decreases. According to study [25], when a uniform and dense oxide film is formed on the surface of carbon steel, the corrosion current density on its surface will stabilize at 0.1 \(\mu\)A/cm\({}^{2}\). Figure 8 shows the variation trend of the self-corrosion current density (i\({}_{\text{corr}}\)) obtained by fitting a Tafel curve during the passivation process. As shown in the figure, the self-corrosion current undergoes a sudden change from 0.629 \(\mu\)A/cm\({}^{2}\) in the first three days of the soaking test to 0.1 \(\mu\)A/cm\({}^{2}\). This suggests that after 3 days of the soaking test, the dynamic parameters of the oxide film are basically stable, but they become even more stable after 5 days. These results provide important insights into the passivation process of carbon steel in a simulated concrete environment. The decrease in the anode Tafel slope and increase in the corrosion potential observed with the increasing soaking time indicate the formation and stabilization of an oxide film on the steel surface. This suggests that the steel reinforcement electrode becomes increasingly passive as time passes. The stabilization of the oxide film is accompanied by a significant decrease in the anode reaction activity of the steel working electrode, which is beneficial for its long-term durability in concrete structures. This information can guide engineers and researchers in developing appropriate strategies to mitigate corrosion-related issues and ensure the long-term durability of concrete structures. For example, cathodic protection technology can be used to make steel bars become the cathode of a battery through external currents, thereby suppressing the occurrence of corrosion reactions.