What is Anodized Aluminum
Aluminum is a very widely used metal. Due to its lightness, it is used to make very many things. Usually, metals are destroyed by the process of oxidation. However, aluminum can be shielded from this process through anodizing. Anodizing is a process that aims at making aluminum stronger and more durable. When aluminum alloys are anodized, resistance to corrosion and surface hardness increases. In addition, the anodized aluminum can be dyed and its lubrication and adhesion properties are improved. How is anodized aluminum made? When pure aluminum gets exposed to air or any oxygen containing gas at room temperatures, it passively becomes anodized to form a 2 to 3 nanometer thick amorphous surface layer of aluminum oxide.
The surface layer forms very effective protection against corrosion. Aluminum alloys form a larger oxide layer (5 to 15nm thick) than pure aluminum when they undergo passive anodizing. However, they are not as resistant to corrosion as pure aluminum oxides. The corrosion resistance of aluminum alloys is especially decreased by certain impurities such as iron, copper and silicon. Aside from the natural oxidization of aluminum, aluminum and its alloys can be anodized chemically in order to increase corrosion resistance. The process of anodizing involves placing the aluminum sheet to be anodized in a chemical acid bath. This is usually carried out in laboratory experiments and the chemical used is acetone in most of the cases.
The sheet of aluminum acts as the positive anode during the anodizing process while the chemical acid bath will act as the negative cathode. An electric current will then be passed through the acid bath. The current causes the surface of the aluminum to rust or oxidize forming a strong coating on the surface that replaces the surface aluminum. The resulting aluminum is what is referred to as anodized aluminum. How can anodized aluminum be made stronger? Under the right circumstances, anodized aluminum can be almost as hard as diamond. However, the anodizing process does not protect the aluminum fully. In some instances, the anodizing process will leave micro fissures in the coating which can predispose the aluminum to corrosion.
The coating is also prone to chemical dissolution in very high or very low PH. In such cases, the anodized aluminum can be electroplated to make it more corrosion resistant. Some of the most popular processes used to increase corrosion resistance in the anodized aluminum are precipitating or hydrothermal sealing. Uses of anodized aluminum As aforementioned, anodized aluminum is very useful in places that require to use corrosion resistant metal. As such, it is used to make protective shields for satellites, in the automobile and aircraft industry and in making kitchen ware. It is also used by furniture makers in making the frameworks of lamps, decorative items and outdoor items.