Effect of Functionalized MWCNTs/Ag on Corrosion and Fouling Resistance of Epoxy Coatings

The work aims to study the effects of MWCNTs/Ag@PDA composites on the structure, mechanical properties, corrosion resistance and antifouling properties of water-based epoxy resin coatings. In this experiment, MWCNTs were used as carrier loaded silver nanoparticles and then modified with PDA. Finally, the composite powder was added to the water-based epoxy resin to improve its mechanical properties, corrosion resistance and antifouling properties. The results of XRD, Raman, XPS and SEM showed that Ag particles were loaded on MWCNTs and modified by PDA. MWCNTs/Ag@PDA composites were successfully prepared. The results of the binding force test showed that the adhesion of the composite coating was improved compared with that of blank coating after addition of composite powder. Among them, MAP/WEP coating had the best adhesion of 4.29 MPa. The corrosion resistance mechanism of fillers in coatings could be analyzed based on the nitrogen brittle cross-section morphology of coatings, EIS test of coatings, and fitting results of EIS test data. In the SEM results of nitrogen embrittlement cross section, there were obvious shrinkage holes in the section of the blank coating. After the addition of MWCNTs/Ag, the density of the epoxy coating became higher, but the agglomeration of MWCNTs/Ag and poor compatibility with the coating led to defects in MA/WEP. However, PDA improved the dispersion of MWCNTs/Ag in the epoxy resin, resulting in a higher density coating without defects. The different coatings were soaked in a 3.5wt.% NaCl solution for 28 d, and then the electrochemical properties of the different coatings were tested by an electrochemical workstation. In EIS tests, MAP/WEP had the largest capacitance arc radius and the largest low-frequency resistance modulus value. At the same time, MAP/WEP had the widest high phase frequency region. The results of the Tafel curve showed that the addition of powder could increase the corrosion potential and decrease the corrosion current density. When MWCNTs/Ag@PDA were added, MAP/WEP had the highest corrosion potential (−138.65 mV) and the lowest corrosion current (9.82×10−12 A/cm2), which were consistent with the results of the EIS test. In the antifouling test, different coatings were immersed in a seawater solution of Phaeodactylum tricornutum. High-resolution laser confocal was used to analyze the algae adhesion. The results showed that the fluorescence area ratio of MAP/WEP coating was at least 0.12%, and its inhibition rate reached 88%. Through SEM analysis of the morphology and structure of Phaeodactylum tricornutum on the surface of different coatings, the surface structure of Phaeodactylum tricornutum on the blank coating was complete, but after the addition of composite powder, due to the presence of silver particles in the coating, Ag+ would be released on the surface, thus destroying the structural integrity of the Phaeodactylum tricornutum on the coating surface and making the Phaeodactylum tricornutum on the coating surface inactive. Due to the agglomeration of MWCNTs/Ag, the antifouling properties of MA/WEP were not ideal. However, the dispersibility of MWCNTs/Ag@PDA made MAP/WEP have excellent antifouling properties. In summary, PDA can significantly improve the dispersion of MWCNTs/Ag composite in epoxy resin, and the addition of MWCNTs/Ag@PDA can improve the adhesion of the coating and enhance the corrosion resistance and antifouling properties of the coating. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.