The investigation of corrosion behavior of ZrO2–Al2O3-inhibitor/AA2024 nanocomposite thin film using sol-gel and AHP-TOPSIS method

Abstract

Nowadays, the sol-gel thin films doped with corrosion inhibitor have suggested enhancing corrosion resistance of materials. In the present work, ZrO2 and ZrO2–Al2O3 thin films with benzotriazole (BTA) and cerium nitrate inhibitors were applied on the aluminum alloy substrate by using dip-coating process, and heat treated at 150 °C for 2 h with heating rate of 1 °C/min. Then, the crystalline phase, chemical composition, the microstructure and topography of thin films were evaluated by grazing incidence x-ray diffraction, energy dispersive spectroscopy, field emission scanning electron microscopy, and atomic force microscopy, and the average thickness of thin films was measured by ellipsometry technique. In addition, electrochemical impedance spectroscopy, and potentiodynamic polarization investigations were used to study the corrosion protection properties of thin films. Eventually, the experimental results related to the three independent coating conditions (sample A, B, D) were investigated by analytic hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS). Results indicate the formation of composite thin films without microcracks comparison to the single-component coating, and electrochemical impedance tests after 4 day immersion in the corrosive environment illustrates an improvement of corrosion resistance of sample C (with the first and outside layer of ZrO2 and two middle layers of ZrO2, Al2O3 and BTA) more than 5 times compare to the bare AA2024 aluminum alloy. Additionally a decrease in the corrosion current density from 3.1 μA/cm2 for the uncoated aluminum to 0.2 μA/cm2, which was observed for sample C. Moreover, the data evaluation was studied by AHP and TOPSIS methods, which was presented the best thin films conditions for the sample B (Four layers of ZrO2 – Al2O3- BTA thin films on the AA2024 alloy) which was in good agreement with the experimental results.