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Uses of Anodizing

8/23/2012 7:54:06 AM | by Anonymous


Anodizing is an electrolytic process which provides a metal with a protective and decorative surface, enhancing its visual appeal and working qualities. The metals that can undergo this treatment range over different properties, including metals such as aluminum, alloys, titanium and zinc. The process involves the manipulation of oxide layers on the metals to produce thicker and durable films which increases the metal’s resistance against wear and corrosion, providing the metal with a surface that is more receptive to paint, adhesives and dyes. Anodizing also gives the surface a more appealing look with multicolor effects, along with providing a surface that is smooth and less prone to friction.


Oxide forms on the surface of metals naturally due to their exposure to oxygen and moisture in the atmosphere. Ferrous metals, when exposed to oxygen and atmosphere, deteriorate over time forming rust and eventually being destroyed. However, non-ferrous metals such as aluminum, zinc and magnesium benefit from the oxide layer instead of being destroyed by it. If the layer is thick enough, it can offer corrosion and wear resistance properties to these metals. Due to this principle, many non-ferrous metals can be anodized to provide attractive finishes that also have the capability to withstand corrosion.


Metals can be anodized by having an electric current passed through and electrolyte solution between them (positively charged anode) and a negatively charged cathode. This reaction causes the crystal structure on the anode’s surface to change and a layer of oxide is deposited on the surface of the metal, or in other words anode. This entire process is known as electrolytic passivation. The process also allows a user to have control over it, allowing for manipulation of the thickness of the film formed and other features of the end result anodized metal. As the metal plays the role of an anode in the process, the entire process is therefore known as anodizing. Anodized metals tend to be porous due to their thick coatings, and therefore require a sealing process to ensure that they are corrosion resistant. Anodic films are used to make anodized finishes more durable, which allows the metals to be post treated with paints and dyes.


Aluminium alloys

Amongst metals that can be anodized, aluminium is the most popular choice for anodizing. As aluminium alloys are ideal for constructing various devices, anodizing these alloys make them even more durable. Aluminium alloys that had been anodized have an increased corrosion resistance, surface hardness and can be coloured, have improved lubrication and adhesion. However, these layers that had been anodized are non-conductive.


Pure aluminiums can be self-passive, meaning that they can form surface layers of aluminium oxide by themselves when exposed to areas that contain oxygen and other gases. Aluminium alloys also tend to form oxide layers on their surface that are thicker as compared to those formed by other metals, however being more susceptible to corrosion. Anodizing usually creates very uniform and regular coatings on the surfaces of these metals. However if the coating is uneven even on a microscopic level, it could harm the metal badly, causing it to be prone to corrosion. Also, if the metal is in the presence of high and low pH chemistry, the oxide coating on it can be worn off easily, leaving the metal prone to corrosion. To overcome these problems, care is taken to ensure that the coating on the metal is even throughout with no fissures or more chemically stable compounds are inserted into the oxide layer of the metals. This helps to ensure that the metal would have better resistance against corrosion and wear.



Anodizing is used vastly in the industry for a range of metals to give them better structure and more durability. Anodizing provides manufacturers and users with several advantages; better appearance, increased durability and strength to name a few.

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