Investigating the anti-corrosion behaviors of the waterborne epoxy composite coatings with barrier and inhibition roles on mild steel.

• A waterborne epoxy composite coating integrating barrier/inhibition property was achieved. • h-BN nanosheets took a positive barrier effect on coatings' corrosive protection. • SZP molecules effectively inhibited the corrosive process. • The synergistic effects provided by h-BN nanosheets and SZP molecules were confirmed by EIS and LEIS methods. Herein, we employed the impermeability of hexagonal boron nitride (h-BN) nanosheets and the inhibition property of strontium zinc phosphate (SZP) corrosion inhibitor to prepare h-BN/SZP waterborne epoxy composite coatings and explored their corrosion protection performance while immersed in 3.5 wt% NaCl solution. On the basis of lip-lip interaction between hexagonal boron nitride, the h-BN nanosheets were exfoliated to a few layers and functionalized with 3-aminopropyltriethoxysilane (APTES). The anti-corrosion performance of the as-prepared waterborne epoxy composite coatings applied on mild steels was evaluated using potential and impedance measurements, fitted pore (pinhole) resistance and salt spray. The corrosion products and the localized electrochemical impedance spectroscopy (LEIS) analysis of the synthesized (Fh-BN, SZP)/EP coating suggested that the superior corrosion resistance of the coated mild steel was attributed to a synergetic effect between physical barrier role of h-BN and inhibition of SZP. Our strategy provides a new protection method in coatings for metallic substrates and will ameliorate the basic research and industrial applications of h-BN nanosheets. [ABSTRACT FROM AUTHOR]