pH-triggered self-inhibition epoxy coating based on cerium-polyphenolic network wrapped carbon nanotube

Self-inhibition ability is crucial to realize long-term anticorrosion performance of coatings. Here, we synthesized a kind of nanofiller made of Ce-III-tannic metal-phenolic network wrapped carbon nanotubes (Ce-III-TA-CNTs). Through incorporation of the nanofiller, the intelligent epoxy coating possessing excellent anti-permeability and pH-responsive self-inhibition performance was investigated in detail. The pH-responsive release activity of Ce3+ ions from Ce-III-TA-CNTs nanoparticles showed an increase trend in the acidic solution of pH = 7 down to 3, and increased first and then decreased in the alkaline solution of pH = 7 up to 11 by UV-vis spectroscopy. The cumulative release amount was above 90 % both at pH = 3 and pH = 9. In addition, the Ce-III-TA-CNTs/EP composite coating system on aluminum alloy showed long-term excellent corrosion resistance proved by accelerated cyclic ageing tests. The coating resistance of EP composite coatings with 1.0 and 2.0 % Ce-III-TA-CNTs loading could maintain above 10(7) Omega.cm(2) after 8 ageing cycles, which was higher than 1.0%CNTs/EP and pure EP coatings. Adhesion investigation indicated that the higher adhesion strengthen (6.7 MPa) and remarkable antipeeling property were recorded for 1.0%Ce-III-TA-CNTs/EP. Moreover, the scratched coating system loaded with Ce-III-TA-CNTs researched by local electrochemical showed long-lasting self-inhibition and anti-diffusion properties with vertical bar Z vertical bar(10Hz) value above 2 x 10(5) Omega.cm(2), potential and current about -0.82 V and 10(-8) A.cm(-2) respectively surrounding the scratched area after 28 days immersion. The results indicated that the synergistic corrosion resistance effect of Ce-III-TA-CNTs came from the cross-linking barrier of CNTs, the active release of Ce3+ inhibitor via pH variation and the rust conversion of tannic acid.