Aluminum is naturally grown in the atmosphere, and aluminum oxide film is formed on the surface to protect metal, so it has excellent corrosion resistance. Therefore, demand for vehicles, ships, and aircraft parts which are widely used in household appliances and building materials and lightweight . An example of such an aluminum surface treatment is anodizing. Anodizing is also excellent in decorative property because it can improve the corrosion resistance, abrasion resistance and surface hardness of metal by making a hard oxide film on the metal surface by electrochemically treating the surface of metal, and various colors can be realized.
The factors affecting the anodizing film formation process include the type of electrolyte, concentration, temperature, current density, voltage, and alloy composition of the metal. Among these factors, this study examined the influence of the alloy component contained in the aluminum alloy on the formation characteristics of the anodizing film.
Among the formation characteristics of the anodized film, the growth rate of the film, defect formation of the film, and color change of the film were examined. The materials used in the experiment were Al6061, Al6063 and Al6082, which have different contents of alloying elements among the Al6000 series which is most used in the industrial field. Experiments were carried out in 20% sulfuric acid solution at 0 ℃ using constant current method and constant voltage method.
As a result of the experiment using the constant current method, the growth rate of the film was not significantly different for the three materials. In the constant voltage method, the growth rate of the film was proportional to the amount of charge flowing for each material. In the order of Al6063 - Al6061 ? Al6082, the film growth rates were observed to increase. In the constant voltage method, the content of the alloy element was small, and the higher the pure aluminum content, the faster the film growth rate was.
Experimental results on the defect and color change of the anodizing film show that Al6082 is the fastest material in color change and Al6063 is the material that is the most rapidly destroyed. It can be seen that the higher the content of the alloy element in the alloy component, the faster the defect of the film occurs. On the contrary, the higher the content of pure aluminum, the better the production efficiency of the anodizing film.
The change in color of the film was more and more darker as time progressed in all three materials, with varying degrees of color change. It was found that the color of the coating film was darker in the case of a material having a large amount of metal element,
In this study, it was confirmed that the anodizing film formation characteristics such as the growth rate, defect formation, and color change of the anodizing film are greatly influenced by the content of the alloying element and the content of pure aluminum.