Preparation and corrosion resistance of ZnO@ZIF-8-SA film on carbon steel surface

Abstract

ZnO@ZIF-8 films were prepared on Q235 steel surface through solvothermal reaction by pre-electrodepositing ZnO films and modified with stearic acid (SA). The surface morphology, elements content, crystal structure and chemical structure of films were studied by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The wettability of films was measured by water contact angle meter. The corrosion behavior of films was tested by Electrochemical tests. ZnO films show hexagonal nanotubular morphology, having the best compactness and corrosion resistance at deposition current density of 2.3 mA/cm2 with the protection efficiency of 90.11%. After solvothermal reaction, ZIF-8 grains are formed and clad ZnO nanotubes, forming a contact film to prevent corrosive ions attacking steel efficiently. ZnO@ZIF-8 films have the best compactness and corrosion resistance at Zn2+ concentration of 0.06 mol/L with the protection efficiency of 99.83%. But the corrosion resistance of ZnO@ZIF-8 film declines quickly for the water molecules can get inside the film and destroy the bond between ZIF-8 grains. Thus, SA was grafted to ZnO@ZIF-8 film to enhance its hydrophobicity. After SA modification, the protection efficiency reaches 99.99% and maintains at 95.29% after 14 days immersion in the solution of 3.5 wt.% NaCl.