铝合金钛锆转化处理过程中铝离子的影响及消除

Effect and removal of aluminum ions in titanium/zirconium-based conversion treatment of aluminum alloys

探讨了转化液中铝离子含量对钛锆转化膜性能的影响。采用扫描电镜和能谱仪表征了膜层的微观形貌和成分,并用极化曲线和硫酸铜点滴腐蚀试验评价了其耐蚀性。结果表明:当转化液中铝离子质量浓度为60 mg/L时,所得膜层的形貌最平整致密,耐蚀性最好。但当铝离子质量浓度达到90 mg/L时,膜层表面开始出现"蚀坑",并且随着铝离子含量增加而增多,造成耐蚀性下降。当铝离子质量浓度为210 mg/L时,铝合金表面不能成膜。采用氟化钠去除转化液中的铝离子之后,膜层的耐蚀性恢复到原工艺水平。

The effect of aluminum ions content in conversion bath on the properties of titanium-zirconium conversion coating obtained therefrom was studied. The micromorphology and composition of the coating were characterized by scanning electron microscope and energy-dispersive spectroscope, and its corrosion resistance was evaluated by polarization curve measurement and copper sulfate dropping corrosion test. The results showed that the coating obtained with 60 mg/L aluminum ions in conversion bath has the most levelled and compact surface, and best corrosion resistance. However, when the mass concentration of aluminum ions reaches 90 mg/L, the pits are emerged on the surface of the coating, and grows more and more with the increasing of aluminum ions content, resulting in the decrease of corrosion resistance. When the mass concentration of aluminum ions is up to 210 mg/L, no coating is formed on aluminum alloy. After using sodium fluoride to remove aluminum ions, the coating＇s corrosion resistance returns to the original level as expected.