稀土硝酸盐促进的铝合金锌系磷化成膜过程

采用扫描电镜(SEM)、X射线衍射(XRD)及能谱(EDX)和电化学测试的方法,研究了稀土硝酸盐(REN)对6061铝合金锌系磷化成膜过程的影响,结果表明,少量的稀土硝酸盐添加到磷化液中可以提高磷化成膜速度和细化晶粒,改变磷化膜的组成,但稀土硝酸盐本身并不构成磷化膜的组成成分,它实质上是具有良好载氧能力的促进剂,具有良好的成核促进作用和阴极去极化作用.与在不含稀土硝酸盐的磷化液中所形成的磷化膜相比,铝合金在含有稀土硝酸盐的磷化液中所形成的磷化膜具有较低的化学活性,其耐蚀性得到提高,在所研究的工艺条件下,最佳硝酸盐含量为20～40 mg/L.

Zinc Phosphating Accelerated by Rare Earth Nitrate on Aluminum Alloy

The influence of rare earth nitrate (REN) on the zinc phosphate coatings on aluminum alloy was studied by means of scanning electron microscopy (SEM),X-ray diffraction (XRD),energy-dispersive X-ray (EDX) and electrochemical measurements.The results showed that REN possessed good capacity to transport oxygen and debase polarization of cathode,and markedly accelerated phosphate deposition and consumedly decreased zinc phosphate crystal size.The chemical composition of zinc phosphate coatings varied as the REN concentrations of the phosphating solutions changed,but REN was not incorporated into zinc phosphate coatings.The phosphate coatings formed in phosphating solutions with REN had lower chemical reactivity than those formed without REN,and the corrosion resistance had been improved.