AZ91镁合金表面液相沉积NiO薄膜的耐腐蚀性能

Corrosion Resistance of Nickel Oxide Film Prepared on Magnesium Alloy Surface by Liquid-Phase Deposition

过去,对镁合金表面液相沉积氧化物薄膜的研究不多。为了提高镁合金的耐腐蚀性能,以液相沉积法在镁合金表面制备了一层致密的NiO薄膜。采用扫描电镜观察了NiO薄膜的截面和表面形貌;采用X射线衍射仪分析了其成分;通过动电位极化曲线和交流阻抗谱研究了不同沉积时间所得NiO薄膜的耐腐蚀性能。结果表明:随沉积时间的延长,NiO薄膜由花瓣状变为网络交织状,厚度逐渐增加,膜中NiO含量增加,但5 h后增加不明显,膜层致密性及耐蚀性先增加后降低;沉积5 h所得NiO薄膜表面光滑,为致密网状,防腐蚀性能最好,与AZ91镁合金基体相比,其腐蚀电位正移了706 mV,自腐蚀电流密度降低了1个数量级。

Compact NiO film was prepared on the surface of AZ91 Mg alloy by liquid-phase deposition so as to improve the corrosion resistance. The surface and cross-section morphology of as-prepared NiO film were observed with a scanning electron microscope,and its composition was analyzed with an X-ray diffractometer. Moreover,the corrosion resistance of NiO films obtained at different deposition duration was evaluated based on measurements of potentiodynamic polarization curves and electrochemical impedance spectra. Results indicated that the petal-shaped appearance of as-prepared NiO film tended to be transformed to intertwined net-like appearance with extending deposition time,its thickness gradually rose therewith,and its compactness and corrosion resistance initially rose but decline later therewith. However,as the deposition time was above 5 h,the thickness of the NiO film assumed little variation with varying deposition time. Particularly,NiO film obtained at a deposition time of 5 h was smooth and had dense net-like appearance as well as excellent corrosion resistance. Namely,as compared with Mg alloy substrate,the corrosion potential of resultant NiO film was positively shifted by 706 mV while its corrosion potential was reduced by 1 order of magnitude.