Polyethylenimine wrapped mesoporous silica loaded benzotriazole with high pH-sensitivity for assembling self-healing anti-corrosive coatings

Abstract

The aim of this work is to develop a self-healing coating doped with pH-sensitive nanocontainers for the active corrosion protection of mild steel. A pH-sensitive carboxyl-functionalized mesoporous silica nanomaterials (MSNs-COOH) was prepared via chemical modification of mesoporous silica nanomaterials (MSNs) which was synthesized in a tetraethyl orthosilicate (TEOS) solution via base catalyzed sol-gel process. Benzotriazole (BTA) molecules were loaded into the internal pores of the prepared MSNs-COOH. Then the BTA-loaded MSNs-COOH were wrapped by the highly branched polyethylenimine (PEI) to obtain the nanocontainers of BTA@MSNs-COOH-PEI. SEM, TEM, DLS, XRD, nitrogen adsorption-desorption isotherms, TGA and FT-IR analyses were employed to characterize the as-prepared nanocontainers. The pH-sensitive releasing property of BTA@MSNs-COOH-PEI was studied using UV–vis spectroscopy, which indicates that the releasing rate of BTA from BTA@MSNs-COOH-PEI can be accelerated under alkaline conditions. Afterwards, a self-healing coating was fabricated based on the epoxy resin primer doped with BTA@MSNs-COOH-PEI which can release BTA inhibitor once localized corrosion occurs. Finally, the active anti-corrosion performance of the as-prepared coating was confirmed by EIS measurements and salt spray tests. The self-healing coating prepared in this work brings a new sight for elaborate design of active anti-corrosion coatings.