Research on BN-based waterborne anticorrosive coatings integrating long-lasting anticorrosive, high cross-linking and self-healing properties

Porosity and cracks during the curing process of waterborne epoxy resins have severely limited their application. In this study, Zn2+ was adsorbed on the surface of BN through a coordination reaction. And the electronegativity difference between Hexamethylene diamine tetramethylene phosphonic acid (Hdtmp) and Zn2+ was exploited to make it forming a stable complex on the surface of BN. Corrosion-resistant composite coatings were prepared by doping the synthesized BN@Zn-Hdtmp hybrid materials into waterborne epoxy resin. The anticorrosion mechanism and anticorrosion properties of the BN@Zn-Hdtmp hybrid materials were predicted by molecular dynamics and density functional theory. Furthermore, after immersion in a 3.5 % NaCl solution for 45 days, the BN@Zn-Hdtmp/EP composite coating exhibited a significant decrease in resistance, from 3.371 × 109 Ω cm2 to 1.845 × 107 Ω cm2. This represents a two-order-of-magnitude enhancement in resistance compared to pure EP. Additionally, the surface roughness of the carbon steel coated with BN@Zn-Hdtmp/EP was found to be lower than that of EP. EIS analysis of scratched coatings, salt spray tests, SEM images of the corroded areas and quantitative EDS spot scan analyses showed that the composite coatings have excellent self-healing properties. The crosslink ability between BN@Zn-Hdtmp and EP was demonstrated by DFT calculations as well as TGA tests to provide a new crosslinking mode and enhance the densification of EP. In the mechanical property tests, the tensile strength, elongation at break, and adhesion of the composite coatings were better than those of pure EP. The above results indicate that BN@Zn-Hdtmp/EP has excellent anticorrosive and mechanical properties, which provides a new method to achieve long-lasting anticorrosive protection of waterborne epoxy resin.