Incorporation of layered double hydroxides modified with benzotriazole into an epoxy resin for the corrosion protection of Zn-Mg coated steel

Abstract

An epoxy coating loaded with inhibitor nanoreservoirs was elaborated for the smart corrosion protection of Zn-Mg coated steel (ZM). To achieve this, Mg-Al layered double hydroxides modified with benzotriazole (LDH-BTA) were synthesized using the coprecipitation method. LDH, without and with BTA, were characterized by using X-ray diffraction, scanning and transmission electron microscopy, Fourier transformed infrared spectroscopy and total organic carbon measurements. The effect of LDH-BTA on the corrosion inhibition of Zn-Mg coated steel in immersion in chloride solutions was studied by means of electrochemical techniques and surface analyses. The stability of a suspension made of epoxy resin loaded with 1.5 wt. % LDH-BTA was controlled by sedimentation measurements using Turbiscan, whereas the corrosion protection abilities of the composite coating were assessed by focusing on both barrier and self-healing properties. It was shown that the BTA molecules present on the LDH surface are released in the presence of chloride ions, thus interacting with the metallic surface and improving the corrosion resistance of ZM. The suspension composed of epoxy resin and LDH-BTA was proved to be stable due to the organic functionalization of LDH by the BTA organic inhibitor. The modification of LDH with BTA allows the reasonable barrier properties of the epoxy-based coating associated with a self-healing ability in immersion conditions to be maintained.