Influence of pH on the growth behaviour of Mg–Al LDH films

In this work, a facile in situ method to prepare the Mg-Al layered double hydroxide (LDH) films on an anodised AZ31 substrate was proposed. The morphology, structure and composition of the LDH films produced within a range of pH values were studied by scanning electronic microscopy, X-ray diffractometer, energy-dispersive spectrum and Fourier transform infrared. The corrosion behaviours of the LDH films were further investigated using electrochemical impedance spectroscopy and potentiodynamic polarisation. The influence of pH on the LDH films was also studied. The results revealed that the pH of solution is important in the formation of the LDH. The films, which formed within the pH range from 10.72 to 11.72, possessed higher crystallinity and denser layered structure. These LDH films could effectively seal the anodic oxide films and enhance the corrosion resistance of the AZ31 substrate.