Improved performance of epoxy resin coating with the modification of dopamine doped Ti₄O₇

In this paper, a dense and well‐adherent polydopamine‐Ti 4 O 7 /epoxy resin (PDA‐Ti 4 O 7 /EP) composite coating is successfully prepared. The modified grafting of Ti 4 O 7 by polydopamine (PDA) is achieved through the coordination complexation of unstable catechol groups in PDA with coordination unsaturated Ti atoms in Ti 4 O 7 . The potentiodynamic polarization curve and electrochemical impedance spectroscopy test results show that the performance of the composite coating is improved compared with that of the pure epoxy coating, and the composite coating slows down the penetration of electrolytes and aggressive ions and improves the corrosion resistance. The composite coating with 2 wt.% PDA‐Ti 4 O 7 filler shows the best corrosion resistance, and its | Z | 0.01 Hz remains above 10 11 Ω cm 2 after 30 days of immersion in 3.5 wt% NaCl solution. This can be attributed to the good barrier property of PDA‐Ti 4 O 7 filler, which carries NH 2 and OH reactive groups, interacting with the resin and matrix to improve the dispersion of the filler and the adhesion of the composite coating. The NH 2 group reacts with the epoxy group in the epoxy resin in a ring‐opening reaction, which avoids the agglomeration of the filler and the uniformly dispersed filler fills the pores in the coating due to curing to improve the denseness of the coating and give full play to the barrier property of the filler. At the same time, the hydrogen bonding between the filler and the OH group in the resin and the substrate increases the adhesion of the coating. In addition, the unstable catechol group in PDA chelates with iron ions to further improve the overall corrosion resistance of the coating. Highlights A dense and well‐adherent PDA‐Ti 4 O 7 /EP coating is successfully prepared. PDA connect with Ti 4 O 7 through coordination of catechol groups and Ti atom. PDA‐Ti 4 O 7 are chemically bonded to the EP through a ring‐opening reaction. PDA‐Ti 4 O 7 improves the crosslinking density and barrier ability of the coating.