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Application of Aluminum Anodizing Process in Industry
Aluminum and its alloys are prone to oxidation when exposed to air. The natural oxide layer that forms on the surface is amorphous, which can cause the metal to lose its original shine. Although this thin layer (about 4–5 nm thick) offers some degree of passivation, it lacks density, has high porosity, and poor mechanical properties. As a result, it cannot effectively prevent further corrosion from atmospheric elements.
After anodizing, aluminum and its alloys develop a much thicker, more compact oxide layer—ranging from tens to hundreds of micrometers. This artificial oxide film is then sealed, transforming the amorphous structure into a crystalline one while closing the pores. This process maintains the metal’s gloss while significantly enhancing its corrosion resistance and mechanical strength. Additionally, dyeing can be applied to create attractive, decorative finishes. Due to these benefits, the anodizing process is widely used in industrial applications.
First, anodizing serves as a protective layer against corrosion. Properly sealed anodized films exhibit excellent stability in atmospheric conditions. Whether formed using sulfuric acid, oxalic acid, or chromic acid, the resulting oxide layers offer strong corrosion resistance. Common applications include household items like aluminum pots, washing machine linings, and especially in aluminum welded or riveted parts, where the chromic acid method is preferred.
Second, anodizing can also serve a decorative purpose. Transparent oxide layers can absorb dyes and pigments, allowing for vibrant colors and intricate patterns. Modern techniques such as multi-layer oxidation, fireworks effects, wood grain simulation, and transfer printing make aluminum surfaces more visually appealing. These colored layers not only enhance aesthetics but also provide additional protection, making them ideal for products like lighters, pens, and handicrafts.
Third, anodizing can create a hard, wear-resistant layer. By adjusting the anodizing parameters in sulfuric or oxalic acid solutions, a thick and durable oxide film can be produced. Its porous structure allows for oil absorption, which improves lubrication and reduces friction. This makes it suitable for components like engine cylinders and pistons in vehicles and machinery.
Fourth, the oxide layer acts as an effective electrical insulator. Aluminum oxide has high resistivity, and the insulation quality increases with film thickness. This property is valuable in electrical applications, such as capacitors and cable jackets. In some cases, phenolic resin is used to fill the pores, boosting the breakdown voltage. This technique is particularly popular in foreign markets, offering better performance than traditional plastic coatings.
Fifth, anodized layers serve as an ideal base for painting and electroplating. The porous structure enhances adhesion between the oxide layer and subsequent coatings, making it suitable for both paint and metal plating applications.
Finally, anodizing plays a key role in modern architecture. Electrolytic coloring has become increasingly popular for architectural aluminum profiles. It offers a range of colors, including bronze, black, and red, while maintaining excellent wear resistance and color fastness. Unlike traditional methods, electrolytic coloring retains its color even after decades of exposure, making it a superior choice for building windows, doors, shop displays, and more.