Characterization of calcium-modified zinc phosphate conversion coatings and their influences on corrosion resistance of AZ31 alloy
Characterization of calcium-modified zinc phosphate conversion coatings and their influences on corrosion resistance of AZ31 alloy
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DOI：
10.1016/j.surfcoat.2010.11.027
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发表时间：
2011-02
影响因子：
5.4
通讯作者：
R. Zeng;Zi-Dong Lan;Linghong Kong;Yuanding Huang;H. Cui
中科院分区：
文献类型：
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作者：
R. Zeng;Zi-Dong Lan;Linghong Kong;Yuanding Huang;H. Cui
在磷酸盐浴中，在AZ31合金表面制备了磷酸锌涂层和磷酸锌钙涂层两种磷酸盐转化膜。使用扫描电子显微镜观察这些涂层的形态。利用能量色散X射线光谱、X射线光电子能谱和X射线衍射对其化学成分和结构进行了表征。采用动电位极化技术评价涂层的耐腐蚀性能。结果表明，花状Zn-Ca磷酸盐转化膜主要由磷锌矿(Zn3(PO4)2·4H2O)组成。它们的形态与由 MgO、MgF2、Zn 或 ZnO 和磷锌矿组成的干河床状磷酸锌涂层完全不同。锌和磷酸锌钙涂层均能显着降低基体的腐蚀电流密度。 Zn-Ca镀层比Zn镀层具有更好的耐腐蚀性能。将钙引入磷酸盐浴中会导致 Zn-Ca 涂层完全结晶。
Two kinds of phosphate conversion coatings, including zinc phosphate coating and zinc–calcium phosphate coating, were prepared on the surface of AZ31 alloy in phosphate baths. The morphologies of these coatings were observed using scanning electron microscopy. Their chemical compositions and structures were characterized using energy-dispersive X-ray spectrum, X-ray photoelectron spectroscopy and X-ray diffraction. The corrosion resistance of the coatings was evaluated by potentiodynamic polarization technique. The results show that the flowerlike Zn–Ca phosphate conversion coatings are mainly composed of hopeite (Zn3(PO4)2·4H2O). They have a quite different morphology from the dry-riverbed-like Zn phosphate coatings that consist of MgO, MgF2, Zn or ZnO and hopeite. Both of the zinc and zinc–calcium phosphate coatings can remarkably reduce the corrosion current density of the substrates. The Zn–Ca coating exhibits better corrosion resistance than the Zn coating. Introduction of calcium into the phosphate baths leads to the full crystallinity of the Zn–Ca coating.