采用析氢实验及Tafel极化曲线研究了AZ31B镁合金在不同pH植酸溶液中成膜时的反应速率和转化膜的防腐性能, 并用SEM, AFM, EDS, FTIR观察和检定转化膜形貌、元素组成及官能团构成. 结果表明溶液的pH=1时, 植酸与镁合金的反应剧烈, 转化膜有大量的裂纹; pH=4和pH=6时, 反应速率很慢, 成膜均匀并较少裂纹, 但转化膜较薄; pH=2时, 反应速率较为和缓, 转化膜表面较为平整, 有呈网格状结构的大量细小裂纹, 此时, 所形成的植酸转化膜具有最佳的防腐性能. 此外, 植酸转化膜由较薄的内层及具有一定裂纹的外层所组成, 转化膜含有Mg, Al, Zn, C, O, P元素及PO43-, HPO42-, OH-基团.
The reaction rate of the chemical conversion film fomation process on AZ31B magnesium alloy in phytic acid with different pH values and then the corrosion performance of the conversion films were studied by hydrogen evolution and polarization measurements. The morphology, chemical compositions and functional groups of the conversion films were characterized by SEM, AFM, EDX and FTIR, respectively. The results indicate that phytic acid could tempestuously react with magnesium alloy when pH=1, films with many big cracks are formed on the AZ31B surface. The reaction rate is slower for solutions with pH=4 and 6 than those with pH=1 and 2, the conversion films are uniform but thin. For the solution with pH=2, the reaction rate is mild, the conversion film is uniform and many fine network-like cracks are existed on the surface, which showed superior corrosion resistance rather than those produced in other solutions. Furthermore, the phytic acid conversion film consists of a thin inner lay and an outer layer with cracks. The main elements of the film are Mg, Al, Zn, C, O and P, the functional groups are PO43-, HPO42- and OH-.
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