采用钴盐、高锰酸钾作为化学转化处理液的主要成分,在2024铝合金表面制备了钴-锰复合转化膜;通过正交试验优化了处理液的配方,分析了处理液成分对转化膜面密度的影响;并研究了处理液温度、pH值、处理时间等工艺参数以及润湿剂、促进剂等添加剂对转化膜表面形貌的影响.结果表明:添加高锰酸钾可以提高转化膜的成膜速率;最优处理液配方为10 g·L-1 Co(CH3CO2)2·4H2O,3 g·L-1 KMnO4,4 g·L-1 NaNO3,3 g·L-1氟化物,30 g·L-1 CH3CO2Na;最佳成膜工艺参数为处理液温度50 ℃,pH值7,处理时间20 min;润湿剂、氟化物或钒盐成膜促进剂可改善成膜效果.

A treating bath containing cobalt salt and potassium permanganate was used to produce an environment-friendly Co-Mn composite conversion coating on 2024 aluminium alloy surface.The fomula of the treating solution was optimized with an orthogonal experiment.The influences of solution components on the coating density were analyzed.The effects of the preparing parameters,such as solution temperature,pH value and immersion time,and the additives of wetting agent and accelerators on the surface morphology of coating were also studied.The results show that the potassium permanganate could accelerate the coating deposition on aluminium alloy.The best coating could be produced in the solution composed of 10 g·L-1Co(CH3CO2)2·4H2O,3 g·L-1 KMnO4,4 g·L-1 NaNO3,3 g·L-1 fluoride and 30 g·L-1 CH3CO2Na,and treated at 50 ℃ for 20 min with the pH value of 7.It was also found that the wetting agent and accelerator of fluoride or V salt could improve the coating effect.