Functionalization of h-BN by the exfoliation and modification of carbon dots for enhancing corrosion resistance of waterborne epoxy coating

The amino-functionalized carbon dots (FCDs) were used as intercalators to exfoliate and modify the boron nitride for obtaining the FCDs/boron nitride nanosheets (BNNS) nanocomposite . The FCDs, BNNS and FCDs/BNNS were respectively dispersed into the waterborne epoxy (WEP) matrix to prepare the corresponding modified WEP coatings on the copper substrate through the spray coating method. Their micro/macro-morphologies, compositions, surface roughness , self-healing and corrosion resistance behaviors were comparatively researched. Electrochemical results and surface morphology observation show that WEP FCDs/BNNS coating possesses the optimal corrosion protection performance after 40 d immersion in 3.5 wt% NaCl solution. And the impedance value (4.97 × 10 5  Ω cm 2 ) of WEP FCDs/BNNS coating is still about an order of magnitude higher than that of pure WEP coating (3.36 × 10 4  Ω cm 2 ). In the WEP FCDs/BNNS coating system, BNNS as physical barrier extend the diffusion path of corrosive species and block inherent defects of the coating, thus slowing down the corrosion rate; FCDs as intercalators strip BNNS enhancing its physical barrier effect. Besides, FCDs can also act as the effective corrosion inhibitors , which could adsorb on the exposed or corroded copper surface and hinder the further corrosion. Their synergistic effects of physical barrier performance from BNNS and self-healing capability from FCDs endow the WEP composite coating with outstanding corrosion resistance.