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

Abstract

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 × 105 Ω cm2) of WEP FCDs/BNNS coating is still about an order of magnitude higher than that of pure WEP coating (3.36 × 104 Ω cm2). 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.