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 CeIII-tannic metal-phenolic network wrapped carbon nanotubes (CeIII-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 CeIII-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 CeIII-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 % CeIII-TA-CNTs loading could maintain above 107 Ω·cm2 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 anti-peeling property were recorded for 1.0%CeIII-TA-CNTs/EP. Moreover, the scratched coating system loaded with CeIII-TA-CNTs researched by local electrochemical showed long-lasting self-inhibition and anti-diffusion properties with |Z|10Hz value above 2 × 105 Ω·cm2, 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 CeIII-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.