## Results and Discussion
### Electrochemical Characterization  
The corrosion kinetics of the PGT/WEP coatings with different PDA@GO-TiO\({}_{2}\) content on the surface of the metal body were studied by polarization curves. The polarisation curves of the four nano-PDA@GO-TiO\({}_{2}\) composites PGT/WEP coatings and pure WEP coating after immersion for 7 days are provided in Figure 10, and the parameters extracted from polarization curves after Tafel fitting as shown in Table 1. In usually, corrosion potential is used as a thermodynamic parameter to reflect the thermodynamic state of the coating. Corrosion electro-corrosion potential is used as a thermodynamic parameter to reflect the thermodynamic state of the coating. The more positive the corrosion potential (E\({}_{\text{coor}}\)) represents the better corrosion resistance of the coating. The better the  
Figure 9: Impact resistance (**a**), Pencil hardness (**b**), Adhesion (**c**) of PGT/WEP coatings with different contents of nano-PDA@GO-TiO\({}_{2}\) composites. corrosion current is used as the kinetic parameter, the dynamic state of the coating. The smaller the corrosion current density (I\({}_{\text{corr}}\)) represents the slower the corrosion rate of the coating [50]. From Figure 10, the WEP coating of self-corrosion potential (E\({}_{\text{corr}}\)) was\(-0.656\) V, with the increased of nano-PDA@GO-TiO\({}_{2}\) composites, the self-corrosion potential of PGT-1%/WEP coating was \(-0.514\) V and the PGT-2%/WEP coating was \(-0.437\) V. At the same time, the self-corrosion current (i\({}_{\text{corr}}\)) of the WEP, PGT-0.5%WEP, and PGT-1%/WEP were \(0.314\times 10^{-6}\) A\(\cdot\)cm\({}^{-2}\), \(0.238\times 10^{-}\) A\(\cdot\)cm\({}^{-2}\), and \(0.725\times 10^{-8}\) A\(\cdot\)cm\({}^{-2}\), respectively. The self-corrosion current density of PGT-2%/WEP coating was as low as \(0.418\times 10^{-9}\) A\(\cdot\)cm\({}^{-2}\). However, a clear shift towards negative potentials appear with the further addition of nano-PDA@GO-TiO\({}_{2}\) composites, and the i\({}_{\text{corr}}\) increased to \(0.479\times 10^{-8}\) A\(\cdot\)cm\({}^{-2}\) for PGT-3%/WEP coating. So, the corrosion protection performance against corrosion could be established in the following order: PGT-2%/WEP \(>\) PGT-3%/WEP \(>\) PGT-1%/WEP \(>\) PGT-0.5%/WEP \(>\) pure WEP coating. In addition, the PGT-2%/WEP coating demonstrated a reduction of two or three orders of magnitude in corrosion rate as compared to WEP coating. Electrochemical impedance spectrometry (EIS) to further evaluate the anticorrosive properties of PGT/WEP coatings with different nano-PDA@GO-TiO\({}_{2}\) composites content at different immersion times, as illustrated in Figure 11a-f. In general, the corresponding impedance module that sat under the lowest frequency is utilized in Bode impedance plots. \(|Z|_{0.01}\) could be used as a semi-quantitative indicator of the corrosion resistance of the coating [51]. As shown in Figure 10a-f, for the pure WEP coating, the impedance modulus polts at \(|Z|_{0.01}\) was \(1.39\times 10^{4}\)\(\Omega\cdot\)cm\({}^{2}\) at the 1 day of immersion of 3.5% NaCl. However, the value decreased to \(1.01\times 10^{3}\Omega\cdot\)cm\({}^{2}\) after 15 days of immersion, then reduced \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & \(E_{coor}\)/**v** & \(i_{coor}\)/**A\(\cdot\)cm\({}^{-2}\)** & \(\beta_{a}\)/mV dec\({}^{-1}\)** & \(\beta_{c}\)/mV dec\({}^{-1}\)** & \(\mathbf{R_{p}}\) \\  & & & & & (K\(\Omega\cdot\)cm\({}^{2}\))/E6 \\ \hline WEP & \(-0.656\) & \(0.314\times 10^{-6}\) & 206.79 & \(-209.29\) & 3.327 \\ PGT-0.5\%/WEP & \(-0.573\) & \(0.238\times 10^{-7}\) & 192.49 & \(-203.79\) & 46.098 \\ PGT-1\%/WEP & \(-0.514\) & \(0.725\times 10^{-8}\) & 203.58 & \(-205.17\) & 146.98 \\ PGT-2\%/WEP & \(-0.437\) & \(0.418\times 10^{-9}\) & 209.55 & \(-206.01\) & 2539.43 \\ PGT-3\%/WEP & \(-0.459\) & \(0.479\times 10^{-8}\) & 206.82 & \(-201.12\) & 222.57 \\ \hline \hline \end{tabular}
\end{table}