Effect of Al2O3 and Y2O3 on the corrosion behavior of ZrO2−benzotriazole nanostructured coatings applied on AA2024 via a sol–gel method

Abstract

zirconia-based nanostructured coatings were deposited on AA2024 to improve the corrosion resistance properties. Three different nanostructured coatings, namely, zirconia–benzotriazole, zirconia–alumina–benzotriazole, and zirconia–yttria–benzotriazole, were applied on AA2024 via a sol–gel method using the dip-coating technique. Next, the coatings were annealed at 150°C after each dipping period. The phases and morphologies of the coatings were investigated using grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). The corrosion properties were evaluated using electrochemical methods, including polarization and electrochemical impedance techniques in 3.5wt% NaCl solution. The obtained results confirm the formation of homogeneous and crack free zirconia−benzotriazole-based nanostructured coatings. The average roughness values for zirconia−benzotriazole, zirconia−alumina−benzotriazole, and zirconia−yttria−benzotriazole nanostructured coatings were 30, 8, and 6 nm, respectively. The presence of alumina as a stabilizer on zirconia coating was found to have a beneficial impact on the stability of the corrosion resistance for different immersion times. In fact, the addition of alumina resulted in the dominance of the healing behavior in competition with the corrosion process of zirconia−benzotriazole nanostructured coating.