Study On New Surface Treatment Process Of Aluminum And Aluminum Alloy

As the excellent properties, aluminum is increasingly being utilized in many fields such as automotive, aerospace, electronics and home appliances. On account of bad corrosion resistance and decorative properties, aluminum should be treated before use. Anodizing is one of the means of enhancing the corrosion resistance, wear resistance and decorative properties. But the conventional anodizing processes have some disadvantages, such as complex technique, high cost, and toxic electrolyte of anodizing. A new technology combining anodic oxidation and plasma reinforcing electrochemical deposition was studied in this paper. Additionally, anodizing aluminum film was treated by ac phosphoric pore broadening and the effect of pore broadening on the electrolytic coloring of anodizing film was studied. The main results obtained are presented as follows:(1) The tungstate composite conversion coatings, which were composed of the oxide layer and the precipitate layer, were prepared on aluminum by anodic spark deposition (ASD) technology. This technology combines anodic oxidation with plasma reinforcing electrochemical deposition. The scanning electron microscopy results show that there are many holes with diameter of about 1μm in the film. The film has good apparent quality and corrosion-resistance. In addition, the research result revealed that the degree of protection provided by the ASD coatings is superior to that achieved with other treatments such as chromate treatment and conventional anodic oxidation treatment.(2) Anodizing aluminium film was treated by ac phosphoric pore broadening and influence of ac pore broadening treatment on electrolytic coloring of anodizing aluminium film was investigated in this paper. The results show that, after being treated by ac phosphoric pore broadening, the electrolytic coloring performance of the anodizing aluminium film varies obviously. Anodizing aluminium film with different color such as yellow, gray, green, bronze, blue and so on can be obtained by changing the electrolytic parameters and process conditions. The SEM images show that ac phosphoric pore broadening treatment can double the pore value of the porous anodizing aluminium film. And electrolytic coloring can not affect the surface morphology of the anodizing aluminium film obviously. The optimal ac pore broadening parameters are as follows: phosphoric acid 90～110 g/L, current density 1.5～1.75 A/dm~2, voltage 5～10 V, time 8～12 min, temperature 20～30°C.(3) Ultrasonic power was applied in anodizing of aluminum. Effects of ultrasonic power on the parameters of anodization process and the characteristics of film were investigated. The results clearly showed that growth rate of film, anodization, temperature and current density were increased with the application of ultrasonic power. The porosity ratio of the film prepared with ultrasonic power was lower than that of the oxide film prepared without ultrasonic power, which led to enhancement of the thickness and micro-hardness of the film.