High barrier and durable self-healing composite coating: Boron nitride combined with cyclodextrin for enhancing the corrosion protection properties of waterborne epoxy coating

Abstract

In recent years, a great deal of research has been devoted to designing smart anti-corrosion coatings with diverse self-healing capabilities, effective passive barrier properties, and long-lasting protection. Herein, the tetraethyl orthosilicate (TEOS) was used as a pH response guardian encapsulated on a BTA-loaded β-cyclodextrin (β-CD) nanocavity shells (CD(BTA)@TEOS), which would be ineffective in acidic environments, thus causing the release of BTA. Meanwhile, the polydopamine (PDA) was coated on the hexagonal boron nitride (h-BN) nanosheets (h-BN@PDA) to enhance its dispersibility and provide reactive sites. Further, the h-BN@PDA-CD(BTA)@TEOS (BPCT) hybrids were synthesized by linking CD(BTA)@TEOS nanocavity shells and h-BN@PDA nanosheets through PDA and KH560 as bridging agents. The dispersion of BPCT in waterborne epoxy coating (WEC) can effectively fill the coating defects and prolong the diffusion path of corrosive media, showing excellent barrier properties due to the excellent barrier properties of h-BN@PDA nanosheets against corrosive media. Meanwhile, the excellent self-healing properties of the composite coating under corrosive conditions were mainly derived from the released BTA and stripped PDA in response to pH variation. The corrosion resistance of the composite coating was tested by electrochemical, salt spray tests and microscopic corrosion morphology, and the self-healing properties of the coating were demonstrated by scratch electrochemistry. The expiration time of the BPCT/WEC sample was extended by 15 d, the persistence time in the salt spray test increased by 100 h, and the self-healing properties appeared after 4 h of coating rupture compared to the control WEC. The results proved that the WEC loaded with BPCT nanocontainers had a high barrier effect along with self-healing function and durable corrosion resistance.