Morphology, structure and corrosion resistance of Mg–Al LDH films fabricated in different Al3+ concentration solutions

Abstract

In situ-grown Mg–Al layered double hydroxide (LDH) films were obtained on an anodized AZ31 substrate, with the immersion of sample in different concentrations of Al3+ solution. The structure, composition and morphology of LDH films were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electronic microscopy (SEM), and the corrosion behavior of LDH films was further studied by electrochemical impedance spectroscopy (EIS). The influence of Al3+ concentration on the growth behavior of LDH was also discussed. The results indicated that the nest-like structure of MgAl-LDH film was composed of interconnected MgAl-LDH nanosheets. Besides, the LDH obtained in 0.032 mol·L−1 Al3+ solution, possessing dense laminated structure, could effectively seal the porous surface of anodic oxide film. EIS results revealed that the samples coated with LDH films showed a higher electrochemical impedance, and thus, the corrosion resistance of samples coated with LDH films was signally improved compared with the anodized alloy.