Electrochemical corrosion performance and microhardness of the electrodeposited Ni-CeO2 and Ni-ZrO2 nanocomposite coatings on the AA2219 aluminum alloy

Abstract

Although Ni-based composite coatings have been widely studied, a systematic and direct comparison of the CeO₂- and ZrO₂-reinforced Ni nanocomposite coatings on AA2219 remains limited. Nickel-based nanocomposite coatings are widely used to enhance the surface hardness and corrosion resistance of the A2219 aluminium alloy in chloride-containing environments. In this work, to increase the durability of the AA2219 aluminium alloy, nickel nanocomposite coatings reinforced with varying contents of CeO₂ and ZrO₂ nanoparticles were fabricated on the alloy using composite electroplating. The results demonstrate that the uniform nanoparticle dispersion, particle chemistry, and optimized concentration (3.5 wt%) significantly enhance microhardness from 422 HV for pure Ni to 1089 HV for Ni-ZrO₂ and 1055 HV for Ni-CeO₂. Electrochemical corrosion resistance results for Ni-CeO₂ show a significant reduction in corrosion current density (I_corr) to 1.08 µA compared with 14.7 µA for Ni coatings, and charge-transfer resistance (R_cor) of 25.1 kΩ compared with 0.386 kΩ for Ni coatings, corresponding to a significant enhancement and confirming the strong barrier effect of nanoparticle dispersion. Microstructural characterization and nanoparticle distribution were examined using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), revealing pronounced grain refinement induced by both CeO₂ and ZrO₂ nanoparticles. The key scientific contribution of this study lies in the direct, mechanism-based comparison of CeO₂- and ZrO₂-reinforced Ni coatings deposited under identical conditions, providing new insights into their respective strengthening and anticorrosion mechanisms. These results advance the current understanding of Ni-based composite coatings and provide a useful framework for designing high-performance protective coatings for aluminium alloys for future aerospace coating applications.