Preparation and corrosion resistance of epoxy resin/zinc oxide coating on magnesium alloy surface

Abstract This study focuses on the fabrication and characterization of epoxy resin/zinc oxide (ER/ZnO) composite coatings on the surface of the AZ91 magnesium alloy, aiming to enhance its corrosion resistance in aggressive environments. The research systematically investigated the influence of varying coating ratios on the corrosion behavior of the alloy through a series of hydrogen evolution tests and electrochemical experiments, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Advanced analytical techniques, such as Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), were employed to explore the corrosion mechanism, corrosion morphology, and corrosion rate of both the bare AZ91 substrate and the alloy coated with different ratios of epoxy resin/zinc oxide. Additionally, energy-dispersive X-ray spectroscopy (EDS) was utilized to analyze the elemental composition and distribution within the coatings, providing further insights into the protective mechanisms. The results of this study demonstrate that all ratios of epoxy resin/zinc oxide coatings significantly enhanced the corrosion resistance of the magnesium alloy compared to the uncoated AZ91 substrate. The improvement in corrosion resistance is attributed to the synergistic effects of the epoxy resin's barrier properties and the zinc oxide's ability to inhibit corrosion through its inherent chemical stability and filler effect. Furthermore, it has been observed that the corrosion resistance of the coating increases with an increase in the concentration of zinc oxide as higher ZnO content leads to a denser and more uniform coating structure, which effectively blocks the penetration of corrosive agents. The study also reveals that the optimal coating ratio provides a balance between mechanical integrity and corrosion protection, ensuring long-term durability under harsh conditions. This research not only provides a comprehensive qualitative and quantitative analysis of the corrosion resistance exhibited by AZ91 substrates and alloys with various coating ratios but also proposes an effective surface protection strategy for the application of the AZ91 magnesium alloy in demanding environments, particularly those encountered in marine and industrial settings. The findings highlight the potential of epoxy resin/zinc oxide coatings as a cost-effective and scalable solution for improving the performance of magnesium alloys in corrosive conditions, thereby extending their service life and expanding their range of applications.