## 3 Results and Discussion
### Corrosion Resistance Evaluation
#### 3.2.6 The Equivalent Circuit R(C(R(Q(R(CR)))))  
The equivalent circuit shown in Figure 8 describes a three-layer physical state, which is suitable for the C45 phosphate and painted steel samples immersed in all three corrosion environments. In this case, the surface layer is the paint film (CL) that has a very low electrical conductivity, very thin, while having high resistance and very high electrical capacity in rainwater. However, in seawater, the paint layer exhibits very low resistance, and it seems that it is rapidly deteriorating. The experimental values obtained for the parameters of this circuit are presented in Table 7.  
The resistance of the porous phosphate layer (PL) is lower for PPS than in the case of the I-Zn sample. This change can be due to the fact that the pores are no longer clogged with compounds from the fire extinguishing solution or with reaction products, because in this case, the reaction rate is very low and the quantity of reaction products is very small. Also, the electrical capacity of this layer is represented by non-ideal capacitors as a consequence of the high surface roughness.  
In rainwater, the charge transfer resistance (R\({}_{\text{ct}}\)) is very high and it can be correlated with the resistance of the other layers, the polarization resistance is very high (R\({}_{\text{p}}\) = R\({}_{\text{ext}}\) + R\({}_{\text{in}}\) + R\({}_{\text{ct}}\) = 10.4 k\(\Omega\)\(\cdot\)cm\({}^{2}\)). In the case of immersion in seawater, R\({}_{\text{ct}}\) has the lowest value and thus the polarization resistance is also very low (R\({}_{\text{p}}\) = 1.22 k\(\Omega\)\(\cdot\)cm\({}^{2}\)), therefore, the paint layer does not provide satisfactory protection in seawater.  
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \multirow{2}{*}{**System**} & \multirow{2}{*}{\(\begin{array}{c}\mathbf{R}_{\text{s}}\text{,}\\ \mathbf{\Omega}\ \text{cm}^{2}\end{array}\)} & \multicolumn{2}{c}{\begin{tabular}{c} **CPE 1** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **R\({}_{\text{ext}}\text{,}\\ \mathbf{\Omega}\ \text{cm}^{2}\end{array}\)**} & \multicolumn{2}{c}{\begin{tabular}{c} **CPE 2** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **R\({}_{\text{ct}}\)** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **W** \\ \(\mathbf{\Omega}\ \text{cm}^{2}\)** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **W** \\ \(\mathbf{\Omega}\ \text{cm}^{2}\)** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **N\({}_{\text{S}}\text{${}^{1}$/cm${}^{2}$}\)** \\ \end{tabular} } & \multicolumn{2}{c}{\
\begin{tabular}{c} **10\({}^{3}\)X\({}^{2}\)** \\ \end{tabular} } & \multicolumn{2}{c}{
\begin{tabular}{c} \(\epsilon_{\text{z}}\)** \\ \end{tabular} } \\ \hline OPS/RW & 28.83 & \(3.16\times 10^{-5}\) & 0.54 & 4753 & \(5.44\times 10^{-5}\) & 0.73 & 3893 & \(5.00\times 10^{-4}\) & 7.8 & 8.8 \\ \hline OPS/FES & 6.69 & \(6.95\times 10^{-5}\) & 0.71 & 271 & \(3.63\times 10^{-5}\) & 0.70 & 4246 & \(8.30\times 10^{-4}\) & 8.8 & 9.4 \\ \hline \end{tabular}
\end{table}
Table 6: The values of the equivalent circuit elements for OPS samples immersed in seawater and fire extinguishing solution.  
Figure 7: The equivalent circuit for a corrosive alloy with kinetic and diffusion evolution of reaction rate II.