Authors: Hui Zhang, Yong Wei Song, Zhen Lun Song
Abstract: NdFeB permanent magnets are highly susceptible to corrosion in various environments. A
new composite coating electrodeposited on NdFeB magnets was investigated in this paper. The Ni
matrix film was firstly electrodeposited on NdFeB surface from watts nickel electrolyte, and then
Ni/Al2O3 composite coating was successively electrodeposited on the Ni film. The microstructures of
electrodeposited Ni coating and Ni/Al2O3 composite coating were observed by scanning electron
microscopy (SEM). The corrosion behavior of Ni coating and Ni/Al2O3 composite coating in 3.5wt%
NaC1 solution was studied by polarization curves and electrochemical impedance spectroscopy
(EIS). The results showed that the Ni coating and Ni/Al2O3 composite coating could both provide
adequate protection to NdFeB substrate. But the free corrosion potential of Ni/Al2O3 composite
coating was more positive and the passivation region was more obvious when compared with Ni
coating. Meantime, the capacitance loop diameter of Ni/Al2O3 composite coating was significantly
larger than that of Ni coating ,which suggested that the anticorrosion resistance of Ni/Al2O3
composite coating was better than electroplated Ni coating.
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Authors: Yu Feng Li, Zhao Po Zeng, Di Wang, Xi Ge Wu, Liang Sheng Qiang
Abstract: Water-based Polyaniline(PANI) emulsion and Fluorocarbon(FC) emulsion were synthesized by emulsion polymerization method. The doped polyanline were characterized by Transmission electron microscope(TEM) and X-ray diffraction(XRD). The results showed the PANI has bar-like shape and local crystallinity. The composite anticorrosion coatings of PANI emulsion and FC emulsion were prepared by mixture in aqueous medium and used for corrosion protection of mild steel. The corrosion protection property of PANI/FC coatings on mild steel was investigated by electrochemical impedance spectroscopy(EIS) and open circuit potential(OCP) technique in 3.5wt%NaCl aqueous solution. The results indicated that the water-based PANI/FC coatings could offer high protection because the impedance values and corrosion potential remained at higher. Scanning electron microscope(SEM) showed that the oxidation film formed on the metal surface and prevent corrosion effectively due to the passive effect of PANI pigment. The anticorrosion coatings are environmental friendly because of water dispersion medium.
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Authors: Hong Yun, Zhi Guo Zhang, Qun Jie Xu, Chen Ying Tan
Abstract: SnO2 coatings were supplied on the surface of 304 stainless steel (304SS) by a sol-gel process followed by hydrothermal treatments at different reaction temperature and time, respectively. The effects of hydrothermal temperature and time in pure water on the anticorrosion performances of the SnO2 films in simulated proton exchange membrane fuel cells (PEMFC) environments were investigated by potentiodynamic polarization curves, open circuit potential-time curves and electrochemical impedance spectroscopy (EIS). It was found that the SnO2 coated 304SS via the hydrothermal treatment showed a better corrosion resistance than the sample without hydrothermal treatment and bare 304SS. The SnO2 coated 304SS hydrothermally treated at 160°C for 3h showed the highest corrosion resistance among the samples. The results have been discussed in terms of surface structure of SnO2 film and its anticorrosion performance in simulated PEMFC environments.
793
Authors: Quan Yao Yu, Ying Xin Zhang, Zhen Zhen Liu, Zhi Xiang Zeng, Xue Dong Wu, Qun Ji Xue
Abstract: The Ni-graphene composite coatings were prepared by electrochemical deposition method, using nickel sulfate and graphene as primary reagents. Pure Ni coatings, Ni-graphene coatings with N2H4 and Ni-graphene coatings without N2H4 were prepared from three different but similar electrolytes. The N2H4 added into the solution is for complexation with NiSO4 to settle the Ni ions. Graphene used in this work is characterized by TEM and HRTEM. The reaction of N2H4 with NiSO4 is characterized by XRD and optical graphs. The composite coatings’ morphology, structure and corrosion resistance were characterized by SEM and Potentiodynamic polarization test, respectively. The results show that well dispersed graphene–nickel coatings can be prepared with N2H4 in the electrolyte. By comparison with the situation that electrolyte without N2H4, graphene agglomerated at the surface of nickel coatings. The grain of the coatings prepared with and without N2H4 shows similar sizes. Ni-graphene coatings exhibit poor anticorrosion property by comparison with pure Ni coatings because of the defects (cracks and roughness on composite coatings with and without N2H4 in the solution, respectively) on the surface of graphene nickel coatings. These results provide a basis viewpoint for the further research of graphene-metallic composite coatings’ anticorrosion effect.
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