Zinc phosphate coatings formed on 6061-Al alloy, after dipping in phosphating solutions containing different amounts of Y2O3（yttrium oxide）, were studied by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and electrochemical measurements. Significant variations in the morphology and corrosion resistance afforded by zinc phosphate coating were especially observed as Y2O3 in phosphating solution varied from 0 to 40 mg/L. The addition of Y2O3 changed the initial potential of the interface between aluminum alloy substrate and phosphating solution and increased the number of nucleation sites. The phosphate coating thereby was less porous structure and covered the surface of aluminum alloy completely within short phosphating time. Phosphate coating was mainly composed of Zn3（PO4）2·4H2O （hopeite） and AlPO4（aluminum phosphate）. Y2O3, as an additive of phosphatization, accelerated precipitation and refined the gain size of phosphate coating. The corrosion resistance of zinc phosphate coating in 3% NaCl solution was improved as shown by polarization measurement. In the present research, the optimal amount of Y2O3 was 10-20 mg/L, and the optimal phosphating time was 600 s.
常温下对6061铝合金表面转化膜进行了研究,分别讨论了Zn2+、PO43-、F-、Fe2+、Ce3+、Cu2+对磷化膜质量的影响,同时通过正交试验和综合评定法确定出了一种不含铬的铝合金稀土磷化液的介质组成及相应的工艺参数。转化膜成分含有Zn、Fe、P、O、Ce的复合磷酸盐,结果表明:此磷化液在常温下,8 m in即可在6061铝合金表面上生成一层均匀、致密、耐蚀性良好的磷化膜。该方法工艺简单,在整个工艺过程中不需要使用铬元素,对环境影响小,具有良好的应用前景。
