Z. Ansari, M. Alizadeh, A. Sadeghzadeh Attar,
Volume 33, Issue 2 (3-2015)
Abstract
In this study, mixed metal oxides Al2O3/MgO/TiO2 coatings with Al/Mg/Ti ratios of 5:1:3 and 2.5:3:4 were coated on AA1100 aluminum by sol-gel method. The surface morphology, phase analysis and the corrosion behavior of the Al2O3/MgO/TiO2 coatings were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and electrochemical impedance spectroscopy measurements (EIS) in 3.5 wt.% NaCl solution. The thermal behaviors, the bonds configuration, and functional groups of the coated samples were studied by thermo-gravimetric and differential thermal analysis (TG-DTA) and Fourier transform infrared spectroscopy (FTIR), respectively. The results demonstrated that heat treatment at
450 °C caused an increase in porosity and coating cracking, finally leading to the decrease of corrosion resistance. The best corrosion resistance was achieved for the sample with Al/Mg/Ti molar ratio of 5:1:3 without any heat treatment. The structure of this sample was amorphous, and heat treatment resulted in crystallization and decrease of the corrosion resistance.
