A sustainable dynamic redox reaction passive film for long-term anti-corrosion of carbon steel surface

CeO 2 was used as the only oxidant for aniline polymerization, and polyaniline (PANI) was grown on CeO 2 surface to form CeO 2 @PANI nanocomposites. SEM and TEM showed that the CeO 2 @PANI composites were nanorods in a core-shell structure. XPS indicated that CeO 2 -core was reduced by aniline into Ce 3+ , which was then captured by the PANI-shell. Then the passive ability of CeO 2 @PANI coating on steels was explored. EIS showed that the impedance modulus of the CeO 2 @PANI coating exceeded 10 8  Ω·cm 2 after accelerated immersion. The SVET and XPS confirmed that PANI polarized the anodic reaction, Ce 3+ suppressed the cathodic reaction, and PO 4 3− formed complex precipitation. Some high-valent metal oxides can directly oxidize the aniline polymerization to form MO@PANI hybrid particles. The cations obtained by the metal oxide reduction can be captured by PANI and participate in passivation together with dopants. This study provides a new kind of nanocomposite fillers that can effectively passivate steel substrates within epoxy coatings for long-time protection.