Preparation of highly efficient self-healing anticorrosion epoxy coating by integration of benzotriazole corrosion inhibitor loaded 2D-COF

[Display omitted] •A new self-healing 2D nanofiller with pH-controlled adsorption and release of benzotriazole (BTH) was prepared.•The 2D nanofiller was 2D covalent organic framework of TpPa-1 and used as container.•The BTA corrosion inhibitor was adsorbed on TpPa-1 thanks to protonation/deprotonation processes.•The 2D TpPa-1 was cross-linked with the epoxy resin (EP).•The BTA/2D TpPa-1/EP coating presented self-healing in NaCl solution and t>60 days. In this work, multi-layer stacked two-dimensional (2D) covalent organic framework of TpPa-1 was synthesized as nanocontainer to fabricate self-healing epoxy coating. The corrosion inhibitor of benzotriazole (BTA) was loaded into porous TpPa-1 (Tp: 1,3,5-Triformylphrogroglucinol, Pa-1: 1,4-phenylenediamine), and the load capacity was further improved by electrostatic adsorption. Then, 0.5wt.% BTA/TpPa-1 and 0.5wt.% TpPa-1 were added to the epoxy coating, respectively. The electrochemical Impedance Spectroscopy (EIS) test shown that after 60 days of immersion, the impedance of the BTA/TpPa-1/EP in low-frequency region was 6.45×108Ωcm2, while the impedance corresponding to the TpPa-1/EP coating was 9.04×107Ωcm2. In addition, in the localized electrochemical impedance spectroscopy (LEIS) test, as the immersion time was extended, the impedance of TpPa-1/EP coating at the defect continued to decrease, while the impedance at the defect of the BTA/TpPa-1/EP coating shown an upward trend, showing self-healing performance. This was due to the pH change when the metal at the defect is corroded, which caused the BTA to be released from the nanocontainer and adhered to the metal surface to form a protective film. The improvement of the anti-corrosion performance of BTA/TpPa-1/EP coating mainly comes from two aspects: (1) The good dispersion of TpPa-1 in EP coating improves the physical shielding effect of the coating; (2) The controlled release of BTA can Realize the continuous formation of the bare metal surface protective layer.