含促进剂HF_2^-的铝合金稀土转化工艺

Process for Preparation of Rare Earth Conversion Films on Aluminum Alloy in the Presence of Accelerating Agent HF_2^-

稀土转化无毒、无污染,但成膜效率低。在以Ce(NO3)3为主盐、KMnO4为氧化剂的稀土转化液中添加HF2-作为促进剂,采用正交试验优化转化液配方,并研究了转化液pH值、成膜时间对膜层厚度、耐蚀性、成分和形貌的影响,探讨了HF2-加速成膜的机理。结果表明:稀土转化最佳工艺为7.5g/LCe(NO3)3,1.5g/LKMnO4,0.1g/LHF2-,成膜时间8min,pH=2.2;HF2-在室温下可大大缩短成膜时间,通过刻蚀、配位、取代及活性改变界面层结构的综合作用加速成膜。

HF-2 was selected as an accelerating agent and introduced into rare earth conversion fluid composed of Ce(NO3)3 as the major salt and KMnO4 as the oxidant.The composition of the conversion fluid was optimized based on orthogonal tests.The effects of pH value and film-formation time on thickness,corrosion resistance,composition and morphology of the conversion films were investi-gated.The mechanism for HF-2 to accelerate formation of films was discussed.Results indicate that the conversion fluid with op-timized composition consists of 7.5 g/L Ce(NO3)3,1.5 g/L KMnO4 and 0.1g/L HF-2.The optimal film-formation time and pH value were determined to be 8 min and 2.2.HF-2 could greatly shorten the time for the conversion films to form,accelera-ting the formation of films via etching,coordinating,replacing and changing the structure of the interfacial layer.