Aluminum Anodization Material Characterization

Aluminum is widely distributed and abundant in the world, accounting for 7.56% of the total weight of the earth's crust. In the crust, aluminum is the third most abundant element after oxygen and silicon. In metal family, aluminum is the second category after steel. Aluminum and aluminum alloys are light metals, with a small density of about 1/3 of steel. The standard electrode potential of aluminum is very low, so it is an active metal and it belongs to unstable element in various media.

Fig.1 The distribution of elements in the earth's crust^[1].

Aluminum and its alloy possess many excellent properties such as high specific heat and low temperature brittleness, and they are non-magnetic. The surface of aluminum can spontaneously form a natural oxide film (2.5-5nm) in the air, which has good corrosion resistance in the general natural environment. However, this oxide film is amorphous, so its structure is loose, thin, porous and has low mechanical strength. In some extreme environments, such as in the ocean, in acid or alkaline environment, the corrosion resistance of the oxide film is poor.

With the constant innovation of science and rapid development of industry, aluminum has become the most widely used nonferrous metals due to its excellent performance. Moreover, the demand for aluminum is increasing. Until now, aluminum has been applied in many areas, such as automobile industry and aircraft industry. When applied in some extreme environments, untreated aluminum and its alloy may be corroded. Therefore, finding a way to improve the performance of aluminum is very important. Aluminum anodization is a desired technology.

Fig. 2 Examples of applications of aluminum and aluminum alloys in different fields.

Aluminum anodization is a process technology, in which aluminum or aluminum alloy product is the anode. Putting the anode in electrolyte solution for electric processing, to form an oxide film on its surface. After aluminum anodization treatment, the products are called anodic aluminum oxide (AAO). Compared to natural aluminum oxide film, this treated oxide film performs excellent corrosion resistance and abrasive resistance.

Professional characterizations are critical when obtaining a new anodic aluminum oxide material. Alfa Chemistry is a professional testing company that can provide many testing services about anodic aluminum oxide. Here are some examples.

• Scanning electron microscope (SEM) and transmission electron microscope (TEM) are very powerful instruments that can reveal the microscopic information of anodic aluminum oxide. The microscopic information is very important for analyzing the chemical and physical properties of anodic aluminum oxide. SEM can be combined with many other instruments to analyze the performance of aluminum products. For example, porosity is a common defect in aluminum permanent mould. SEM and energy dispersive X-ray analyzer (EDS) can undoubtedly confirm the different causes of the pore formation although the pores have similar dimensions^[2].

• X-Ray Diffraction is an instrument that can reveal information of the crystal structure and chemical compositions of materials and thin films. It has been used in aluminum recycling by determining the crystalline silica in refractory alumina.

• Contact angle meter is a professional instrument that can determine the surface wettability. Through this method, we can obtain the surface information about an aluminum sample.

• Electrochemical workstation can be used to measure the Electrochemical Impedance Spectroscopy (EIS) and Polarization Curve of aluminum materials. Furthermore, based on those data, the corrosion resistance performance of the samples can be determined.

Alfa Chemistry is professional in anodic aluminum oxide characterizations. Welcome to contact us for more information at any time. Alfa Chemistry can provide accurate and reliable tests results within the time limit. Please feel free to contact us if you would like us to perform any material testing. Check our instruments list for our capabilities.

References

• Turekian K K, Wedepohl K H. Distribution of the Elements in Some Major Units of the Earth's Crust[J]. Geological Society of America Bulletin, 1961, 72(2):175.

• Kaka D, L. Kova?evi, Terek P, et al. Use of SEM and EDS analysis in the investigation of Al-Si-Cu piston alloy cast porosity[J]. Metalurgija, 2009, 48(3):171-174.