Anodizing aluminum is a popular finishing process because it is durable, attractive and easy to maintain. The anodic coating formed by the process is a natural oxide that protects the underlying metal from corrosion and scratches. It also makes the surface very tough and resilient. – Anodize
Properties of aluminum
Due to its excellent physical and chemical properties such as low specific gravity, high specific strength, excellent ductility, good electrical and corrosion resistance, and easy molding and processing, aluminum alloy has become the second most used metal material after steel.
Aluminum alloy will spontaneously form a dense oxide film under natural conditions, and its thickness is generally below 5nm. Though the natural oxide film on the aluminum alloy surface can be automatically repaired right away after it is damaged, its corrosion protection and wear resistance are limited because of its thin thickness.
Aluminum material is suitable for many forms of surface finishing
In order to meet the requirements of modern industry, it is necessary to apply proper surface treatment to aluminum alloy. We all know that aluminum is commonly used in life and industry, and there are many kinds of surface finish methods for aluminum, usually anodic oxidation finish, micro-arc oxidation finish, chemical conversion finish, electroplating finish, chemical plating treatment or surface organic coating (powder or paint spraying), etc. how to anodize aluminum is the most common surface treatment.
Why is anodizing aluminum “favored”?
The anodizing process of aluminum and aluminum alloy has a wide range of industrial applications, which can be used to prevent corrosion of products or to achieve the dual purpose of protection and decoration, such as electrical insulation layer, wear-protection layer, electroplating base, and spray paint base layer, etc.
1. Protect aluminum parts from corrosion- Anodize
Because the film obtained by anodizing itself was stable enough in the different environments, the anodized film on the surface of aluminum can be taken advantage of as a protective base. The oxide film obtained by anodizing aluminum in chromic acid solution is dense and has good corrosion resistance; There’re larger pores on the anodized film, but the film layer is thicker and has strong adsorption capacity, and its corrosion resistance is also very good if it is properly filled and closed. It is especially noted that the chromic acid anodizing method is particularly suitable for the anodizing of riveted and welded parts.
2. Beautify product appearance
For most aluminum and its alloys requiring surface finishing, chemical or electrochemical treatment followed by anodizing with sulfuric acid soaking can lead to an anodized film of great diaphaneity. The anodized film can adsorb a wide variety of dyes, both organic and inorganic are available, bringing a variety of vibrant colors. Not only is the colored film an anti-corrosion layer, but it’s also a decorative layer. Under some special process conditions, it is also possible to obtain a protective and decorative oxide film with an appearance similar to that of porcelain.
3. As a layer with wear-resistant
Via hard anodizing, a thick and hard Al2O3 film layer can be formed on aluminum and aluminum alloy’s surface. The film has both enough thickness and high hardness, additionally, the roughness is good. Hard and thick oxide films can also be obtained on aluminum products by anodizing in sulfuric or oxalic acid solutions.
The oxide film can reserve lube because of its specialty of being thick and porous, so it can be effectively applied to aluminum products working in the friction state, such as automobile and tractor engine cylinders, pistons, etc. After anodizing, it can greatly improve its wear resistance.
4. Being a layer of electric insulation- Anodize
Aluminum and aluminum alloy products after anodic oxidation of the resulting anodize film do well in resistance, so it has an important role in increasing the electrical insulation of some parts, can be used to prepare the dielectric layer of capacitance with anodic oxidation, can also be used to prepare the surface of aluminum oxide for the insulating layer.
5. Being the base layer of paint
Because of the ability of good adsorption and porosity, it can be used as a base layer for painting, so that the painting film and organic film can be firmly bonded with the product, thus improving its resistance to corrosion.
6. Being the basic finish before electroplating
Before aluminum and aluminum alloy products are plated, a base layer should be treated in advance, and then plating can be performed. Kinds of methods can be used as the base layer, besides zinc plating, zinc dipping, and chemical nickel plating, anodic oxidation treatment is also one of the common solutions.
I believe that through the above 6 points you should understand the reasons for the widespread use of anodic oxidation, which is not only widely used in industry but is also “favored” in the field of technology. Many innovative electronic devices are used in anodizing. In the future, we believe that the aluminum alloy anodizing process will be used in many more applications.