Duplex Coating Combing Vanadate-Intercalated Layered Double Hydroxide and Ce-Doped Sol–Gel Layers on Aluminum Alloy for Active Corrosion Protection

In this study, a duplex coating system (LDH-V/SG-Ce) of vanadate-intercalated layered double hydroxide (LDH) and Ce-doped sol–gel (SG) layers was developed for the purpose of active corrosion protection of the aluminum alloy AA2024. ZnAl-LDH film was grown in situ on the surface of an aluminum alloy using a hydrothermal method and intercalated with V2O74− anions as corrosion inhibitors, and sealed with a Ce (III)-doped silane coating using a sol–gel technique. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses were used to analyze the microstructure, surface functional groups and structure of the LDH-V/SG-Ce film. The uniform and compact silane layer was covered both in the pores and on top of the LDH film. The results of glow discharge optical emission spectroscopy (GDOES) indicated that V2O74− and Ce (III) ions were loaded in the LDH layer and silane film, respectively. The potentiodynamic polarization results showed that the corrosion current density of the bilayer system in the presence of corrosion inhibitors was reduced to 1.92 × 10−8 A/cm2. Electrochemical impedance spectroscopy (EIS) results showed that the LDH-V/SG-Ce duplex coating could provide effective protection for the aluminum alloy after being exposed to a corrosive solution for 14 days