A High−Performance Anti−Corrosive Epoxy Coating Based on Ultra−Thin Hydroxyapatite Nanosheets with pH−Responsive Functions

Abstract

The changes in the working environment have necessitated greater requirements in terms of the long−term anti−corrosion ability of metal anti−corrosion coatings, and the emergence of intelligent coatings has met this demand. A nanocontainer with a hydrophobic inner cavity and hydrophilic outer cavity called β−cyclodextrin (β−CD) was grafted onto the surface of hydroxyapatite (HAp) with a silane coupling agent, encapsulating benzotriazole (BTA) and embedded in epoxy resin to improve the coating anticorrosion performance. The excellent corrosion resistance of the coating in immersion and scratch experiments was derived from the inert protective layer formed by the reaction of the rapidly released corrosion inhibitor with the corrosion products on the metal surface. After 30 days of immersion experiment, the coating could still maintain the low−frequency impedance value of 6.28 × 107 Ω cm2. In this work, the enhancement of the physical barrier function of HAp nanoparticle and the pH−response function conferred by β−cyclodextrin provided the coating with good passive and active acting abilities in corrosive environments, respectively.