Study on Corrosion Resistance of Zn-Al Alloy Coated with Zeolitic Imidazolate Framework-67 Film in 3.5 wt.% NaCl Solution

A zeolitic imidazolate framework-67 (ZIF-67) film was prepared on the surface of a Zn-Al alloy via a secondary seeded growth method. The thickness, adhesion and hydrophobicity of the film were evaluated by coating thickness test, the cross-cut test and water contact angle measurements, respectively. The phase composition and surface morphology of the synthesized film were investigated by x-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy, respectively. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy were employed to evaluate the corrosion properties of the ZIF-67 film-coated Zn-Al alloy in 3.5 wt.% NaCl static solution. The compact, hydrophobic and adhering ZIF-67 films (the thickness of 15.0 ± 1.4 µm) were successfully coated on Zn-Al alloy surface. The Icorr of the Zn-Al alloy-coated ZIF-67 film decreased two orders of magnitude in comparison with that of the Zn-Al alloy substrate. The ZIF-67 film decreases the corrosion rate of Zn-Al alloy, and has good corrosion resistance characteristics. The obtained results indicated that the hydrophobic ZIF-67 film has the potential application for the protection of Zn-Al alloy in 3.5 wt.% NaCl solution.