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Zhu J.,Nanjing University of Aeronautics and Astronautics | Yao Z.,Nanjing University of Aeronautics and Astronautics | Jiang Q.,Nanjing University of Aeronautics and Astronautics | Wei D.,Nanjing University of Aeronautics and Astronautics | And 3 more authors.
Journal of the Chinese Society of Corrosion and Protection | Year: 2013

In order to improve the corrosion resistance of chromium-free Zn/Al coating, three different nanoparticles, eg. SiO2, TiO2 and ZnO were added in the coating respectively to form nano composite coatings. Corrosion properties of the nanocomposite coatings were examined through salt water immersion method and electrochemical method. Furthermore, the microstructure and corrosion products of the coatings were analyzed by means of SEM and EDS. The experimental results showed that the nanoparticles dispersed in the coating in the form of flake structure which formed a more effective physical shield, extending the path of the corrosive medium to substrate. Furthermore, the fine grain strengthening was dominant to make the coating a good shielding property when nanoparticle was added. Tafel curves indicated that the nanocomposite coating with SiO2 possessed the best cathodic protection among three nanocomposite coatings, and the corrosion resistance of three nanocomposie coatings was better than that of the chromium-free Zn/Al coating. Source


Wu X.-F.,Nanjing University of Aeronautics and Astronautics | Yao Z.-J.,Nanjing University of Aeronautics and Astronautics | Wei D.-B.,Nanjing University of Aeronautics and Astronautics | Zhang P.-Z.,Nanjing University of Aeronautics and Astronautics | And 4 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2014

The chromium-free zinc-aluminum coatings on Q235 steels surface were prepared by the dip-coating method, and the TiO2 nanocomposite coatings were also prepared with TiO2 nanoparticles added into the as-prepared films. Finally, microstructure, morphology and composition of the coatings were analyzed by SEM, EDS and XRD, and the corrosion resistance behavior of two coatings was evaluated using rapid ammonium nitrate corrosion experiment and electrochemical experiment. The results show that the coatings exhibited lamellar structure where the pores are partially filled with nanoparticles. After corroding in the 20% ammonium nitrate solution for 4 h, the TiO2 nanocomposite coatings maintains its lamellar structure without obvious spalling, indicating a better corrosion resistance than that of the barely chromium-free zinc-aluminum coating. In a 3.5% NaCl solution, the corrosion current density of the TiO2 nanocomposite coating is 2.476×10-6 A/cm2, which is less than 5. 015×10-5 A/cm2 of the chromium-free zinc-aluminum coating, proving the significant improvement of the corrosion resistance. Source


Yang H.Q.,Nanjing University of Aeronautics and Astronautics | Yao Z.J.,Nanjing University of Aeronautics and Astronautics | Wei D.B.,Nanjing University of Aeronautics and Astronautics | Zhou W.B.,Nanjing University of Aeronautics and Astronautics | And 2 more authors.
Surface Engineering | Year: 2014

The Al-Zn-Si coating was deposited on Q235 steel by thermal spray technology. The corrosion behaviour of the coating in simulated marine environments has been investigated through neutral salt spray test (NSS) and electrochemical test. Furthermore, the microstructure and the morphologies of the coating were detected by means of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The results showed that the coating exhibited a dense homogeneous lamellar microstructure without obvious defects. There were different corrosion periods of the coating in the simulated marine environment, such as dissolution of Zn and Al particles, flocculent morphology, acicular crystals and self-sealing behaviour caused by corrosion products. Ultimately, a dynamic equilibrium was formed between the consumption of the coating and the generation of the corrosion product layer. Moreover, Tafel curves indicated that the Ecorr and Icorr of the coating after NSS were lower than the substrate that had a sufficient driving force of the cathodic protection. © 2014 Institute of Materials, Minerals and Mining. Source

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