Anticorrosive reinforcement of waterborne epoxy coating on Q235 steel using NZ/BNNS nanocomposites

The 5-aminotetrazole@ZIF-7@zinc gluconate/boron nitride nanosheets (NZ/BNNS) nanocomposites were synthesized by a facile one-pot method for anticorrosive reinforcement of waterborne epoxy (WEP) coating. The electrochemical tests and scratch tests show that the incorporation of NZ/BNNS nanocomposite can significantly improve the corrosion protection performance of WEP coating by the synergetic effects of passive and active protection. The impedance modulus at 0.01 Hz of WEP NZ/BNNS coating is about 1–1.5 orders of magnitude higher than that of pure WEP coating during the 288 h immersion corrosion test. The enhanced passive protection mainly derives from the two-dimensional structure and impermeability of NZ/BNNS. NZ/BNNS nanocomposites can prolong the diffusion path of corrosive medium. UV–vis spectra indicate that 5-aminotetrazole inhibitor encapsulated in NZ is stimuli-responsively released under acidic conditions. After the intrusion of corrosive ions on Q235 carbon steel, the hydrolysis of iron ions induces local acidification. NZ nanocontainers dissociate under acidic condition and release the corrosion inhibitors . The adsorption of corrosion inhibitors on the substrate then provides the active protection. Relevant corrosion protection mechanism has been proposed.