## 4 Conclusions  
GO-PANI-PDA nanocomposites were successfully synthesized as an ideal filler to improve the anticorrosion properties of epoxy coatings. The GO-PANI-PDA nanocomposites were characterized by FT-IR, SEM and XRD, which proved that the PDA and GO-PANI were completely incorporated without changing the structure of GO-AN nanocomposites. The corrosion resistance behavior and mechanism of the EP coatings filled with GO-PANI-PDA nanocomposites were systematically studied by EIS, Tafel polarization curves and salt spray experiments. The results showed the EP/GPP21 coating had the best corrosion resistance with the positive corrosion potential (\(-\)0.51 V) shifted compared with that of the EP/GP coating (\(-\)0.64 V). The corrosion current density (3.83 \(\times\) 10\({}^{-8}\) A/cm\({}^{2}\)) was also nearly an order of magnitude lower than that of EP/GP (7.05 \(\times\) 10\({}^{-7}\) A/cm\({}^{2}\)), which corresponded to the lowest corrosion rate of 4.50 \(\times\) 10\({}^{-4}\) mm/year. The salt spray test displayed that EP/GPP 21 coating had over 30-day long-term preservative effect on Q215 steel. Doping GO-PANI in combination with the excellent properties of PDA gives GO-PANI nanosheets better compatibility and dispersion in epoxy resins, strengthening the bonding performance between the coating and the substrate. It can also adjust the electrical conductivity of the material, fill the defects in EP/GP and improve the barrier properties and electrochemical passivation properties of GO-PANI. This work is expected to be widely used in the field of long-term corrosion protection, providing the necessary protection for various marine installations, ships and other metal components.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/polym14163355/s1](https://www.mdpi.com/article/10.3390/polym14163355/s1)]([https://www.mdpi.com/article/10.3390/polym14163355/s1](https://www.mdpi.com/article/10.3390/polym14163355/s1)), Figure S1: XRD patterns of GO, PANI, and GO-PANI; Figure S2: FT-IR spectra of GO and GO-PANI.  
Conceptualization, Y.H. and B.Z.; methodology, J.W.; software, R.H.; validation, Y.H. and J.W.; formal analysis, Y.H.; investigation, B.Z. and Y.H.; resources, Y.H.; data curation, J.W. and B.Z.; writing--original draft preparation, B.Z.; writing--review and editing, J.X. and Y.H.; visualization, J.W.; supervision, R.H.; project administration, Y.H.; funding acquisition, Y.H. All authors have read and agreed to the published version of the manuscript.  
This research was financially supported by the Minjiang Scholarship of Fujian Province (No. Min-Gaojiao [2010]-117), Central-government Guided Fund for Local Economic Development (No. 830170778), R&D Fund for Strategic Emerging Industry of Fujian Province (No. 82918001), Open Fund of Fujian Key Laboratory of New Energy Generation and Power Conversion (No. KLIF-202102), International Cooperation Project of Fujian Science and Technology Department (No. 830170771) and Analytical Testing Fund of Qingyuan Innovation Laboratory of Fujian Province.  
Not applicable.  
Figure 14: The contact angle results of (**a**) EP/PDA and (**b**) EP/GPP coating.