ZIF-8-based micro-arc oxidation composite coatings enhanced the corrosion resistance and superhydrophobicity of a Mg alloy

Abstract

Mg alloys are considered the most promising engineering materials because of their unique properties. However, the uncontrolled corrosion rate of these alloys limits their applications. Therefore, in this study, a micro-arc oxidation layer was used as a transition layer to “directly” grow a zinc-based metal-organic framework (MOF) composite coating on the surface of a Mg alloy (AZ91D). Herein, the two zeolitic imidazolate framework (ZIF-8) coatings with different morphologies were separately prepared by homologous metal oxide induction and a one-step in-situ growth method. The superhydrophobic composite coating showed strong hydrophobicity and self-cleaning properties, which could prevent the penetration of water and corrosive ions (Cl−) into the surface of AZ91D. Electrochemical tests demonstrated that the super-hydrophobic composite coatings greatly enhanced the corrosion resistance of AZ91D, and the corrosion current density decreased from 10−5 to 10−9 A/cm2. These results indicate that the ZIF-8 coatings are beneficial for improving the hydrophobicity and enhancing the corrosion resistance of Mg alloys. Therefore, MOF composite coatings provide a new strategy that can be used to prepare multifunctional anticorrosion coatings on metal substrates.