A smart sol-gel coating incorporating pH-responsive BTA-ZIF-8 MOF assembled hexagonal boron nitride for active/passive corrosion protection of 1060 aluminum alloy

Integration of both passive and active corrosion-protecting mechanisms is an effective method for endowing sol-gel derived coatings with long-term anticorrosion performance. To provide “smart” functionality for sol-gel coating, a novel self-healing nanocontainer is fabricated via the in-situ growth of 1H-benzotriazole-inbuilt zeolitic imidazolate framework (BTA-ZIF-8) on hydroxylated hexagonal boron nitride nanosheets (BN-OH), which exhibits efficient pH-dependent inhibitor release behavior at both acidic and alkaline media. Electrochemical measurements reveal that sol-gel coating containing the BTA-ZIF-8@BN-OH nanocontainers exhibits superior anticorrosion performance and long-term corrosion protective capability, with |Z|0.01Hz increased by nearly three orders of magnitude (∼2 × 108 Ω·cm2) compared to that of pure sol-gel coating after 28 days of saline solution immersion. In addition, the EIS measurements on sol-gel coating surfaces with artificial scratches show increased impedance values after prolonged immersion in saline solution, indicative of effective active inhibiting effect. This phenomenon is the result of the synergistic effect of both passive and active corrosion protection. The active protection (inhibiting effect) is provided by the on-demand release of inbuilt BTA inhibitor from ZIF-8 frameworks, whereas the passive protection (barrier performance) is achieved through the “labyrinth effect” of BN-OH nanosheets as well as the improved interfacial compatibility of nanocontainers with surrounding sol-gel matrix by surface hydroxylation of h-BN nanosheets. This nanocontainer design offers a facile strategy for fabricating self-healing sol-gel coatings with the exceptional anticorrosion properties.