Effect of operating parameters on the structural growth of ZnAl layered double hydroxide on AA6082 and corresponding corrosion resistance properties

In this study, a series of ZnAl layered double hydroxide (ZnAl-LDH) thin films were synthesized on an AA6082 alloy by a single-step hydrothermal process at different synthesis parameters, including reaction temperature, reaction time, pH, and the relation between the LDH structural variations, and the corresponding corrosion resistance properties are briefly reported. The as-prepared synthetic coatings were characterized by scanning electron microscopy and X-ray diffraction. The corresponding corrosion properties were evaluated through potentiodynamic polarization curves and through electrochemical impedance spectra. The findings demonstrated that synthesis parameter variations impart an influential effect on the geometry of LDH, film thickness, and structural morphologies which have a significant  impact on LDH corrosion resistance properties. The ZnAl-LDH corrosion resistance was found to increase with respect to extended high temperature and aging time, while the synthetic pH conditions also promoted LDH growth and film thickness, relative to lower-pH reaction conditions. The optimization results are attributed to high ZnAl-LDH corrosion resistance and act as a strong barrier film and ion-exchange surface area. The ZnAl-LDH films at 80°C-18r-6.5pH have shown much lower corrosion current density compared to bare AA6082, and a decrease of up to five orders of magnitude is observed.