采用水热法在Mg-3Nd-Zn-Zr合金表面制备无铬化学转化膜,研究了乙酸钠对膜层的影响.用场发射扫描电镜、X射线衍射、电化学测试方法分别研究了转化膜的形貌、相组成和耐蚀性能.结果表明,转化膜主要由球形颗粒状和层片状的Mg(OH)2相、以及少量含Si的非晶化合物组成;适量的乙酸钠能促进球形颗粒状和层片状Mg(OH)2发生团聚,缩小层片间隙, 且对转化膜的生长速率影响小; 膜层厚度可以达到约25μm, 与基体结合牢固, 耐蚀性得到明显提高.
A chrome-free chemical conversion film for Mg-3Nd-Zn-Zr alloy by hydrothermal process was studied. The effect of CH3COONa on the properties of the films was then examined. The surface morphology, microstructure and corrosion resistance of the films were characterized by FE-SEM, XRD and electrochemical testing method. The results show that the conversion films mainly consist of granular particles and flakes of Mg(OH)2 phase. A few of amorphous compounds containing Si also are found in the films. Moderate CH3COONa can promote agglomerating of granular particles and flakes of Mg(OH)2 without affecting the growth rate of films, which shrinks the gap of flakes Mg(OH)2, so the porosity of the conversion films is decreased. The thickness of the film which has great adhesion with the substrate can reach about 25 μm, and the corrosion resistance is improved significantly.
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