【作者】 吴海兰；

【导师】 程英亮；

【作者基本信息】 湖南大学 ， 材料加工工程， 2007， 硕士

【摘要】 镁合金是已使用的最轻的金属结构材料,具有高的比强度、比刚度和减震性,易回收等特点,在汽车、电子、航空等领域得到广泛的应用。但是,镁合金的耐腐蚀性较低,应用受到很大的限制。目前,研究镁合金的环保型阳极氧化工艺,提高镁合金的耐腐蚀性能,对促进镁合金的工业应用具有重要的意义和紧迫性。本文探索并优化镁合金的环保型阳极氧化工艺,氧化液中不含Cr、P、F等环境有害成分,获得具有较好防护性能的镁合金表面氧化膜。并对部分影响镁合金阳极氧化成膜过程以及耐腐蚀性能的工艺参数进行了研究,同时对镁合金阳极氧化成膜机理和腐蚀防护机理进行了初步探讨。借助恒流阳极氧化技术通过改变电流密度、时间等工艺参数,制备了不同性能的阳极氧化膜。利用动电位极化技术对所得氧化膜的耐腐蚀性进行测试,对处理时间,电流密度,不同牌号镁合金等因素对镁合金阳极氧化成膜过程及耐腐蚀性能的影响进行研究,结果表明ZK60镁合金在电流密度恒定为10mA·cm^-2时,所得的阳极氧化膜的耐腐蚀性先随着阳极氧化时间的增加而增大,氧化40min时耐腐蚀性能最好。延长氧化时间到60min,膜层的耐腐蚀性反而下降;当电流密度低于20mA·cm^-2时,膜层的耐腐蚀性能随着电流密度增加而增大,而大于20mA·cm^-2时,膜层的耐腐蚀性能随着电流密度的增加而减少。不同牌号镁合金在同样的条件下阳极氧化所得的膜层的耐腐蚀性能也不同,基体合金的性能对氧化膜的耐腐蚀性有着极大的影响。本文还探讨了阳极氧化液中各成分对所得氧化膜性能的影响,利用正交实验对阳极氧化液配方进行了优化,电化学阻抗谱、电化学极化测试结果表明,优化的工艺能显著提高ZK60镁合金的耐腐蚀性能。采用XRD、SEM、EDS对氧化膜膜层成分、形貌和结构进行了分析。利用SEM观察新的阳极氧化工艺与传统的HAE工艺所得膜层的差别。结合力测试结果表明优化工艺所得的膜层与基体金属间有较强的结合力。利用中性盐水浸泡试验和电化学阻抗谱对ZK60镁合金的空白试样和经过阳极氧化处理的试样进行测试,探讨其腐蚀机理。更多还原

【Abstract】 Magnesium alloys, the lightest metal structural material in use, have been widely applied in automotive, electronic and aeronautical industries because of a number of desirable features, such as high specific strength, high specific stiffness, damping characteristic and recycled easily. However, their applications are limited severely for their low corrosion resistance. For the moment, it is quite urgent and significant to search an environment-friendly anodizing process of magnesium alloy, and improve its anti-corrosion property in the industrial application of magnesium alloy.An magnesium alloy anodizing process based on an environmentally friendly electrolyte bath has been studied in this paper. The anodizing process can form a better anti-corrosive anodized film on magnesium alloy. The effects of different processing parameters on anodizing of magnesium alloys were also studied. At the same time, the mechanisms on the formation of anodic film as well as the corrosion and protection properties of anodized samples were studied.Different films were formed by changing the processing parameter using constant current anodizing method. The properties of the films were determined by EIS and potentiodynamic polarization method. The investigation show that when the applied current density is 10mA·cm^-2, the anti-corrosion properties of ZK60 magnesium increase with the anodization time at first, it is the best when the anodization time is 40min, but if the anodization time was longer than 40min, the corrosion resistance of the film decrease. The effect of current density on the properties of the films are also considered, When the current density is less than 20mA·cm^-2, the corrosion resistances of the films increased with current density, but when it exceeds 20mA·cm^-2, the corrosion resistances of the anodized films begin to decrease with current density. The properties of the anodizing films formed on different magnesiums is different, even when the other conditions are the same, and the magnesium itself has an obviously effect on the anodized films.The effect of the electrolyte solution on the protective property of the film was also investigated. Orthogonal tests was applied to select an optimum solution, and the results showed the optimum bath can improved the corrosion resistance of ZK60 magnesium obviously, and the film formed in the optimum bath shows superior corrosion resistance than that formed by the traditional HAE process. Microstructure and composition of films were examined by SEM, XRD and EDS. The cohesion tests showed that the anodizing films had excellent cohesion. The corrosion resistance of both blank sample and anodized samples were determined by neutral salt immersion test and EIS to study their corrosion mechanisms.更多还原