As a lightweight, high-strength and corrosion-resistant metal material, aluminum alloy has been widely used in aerospace, automobile manufacturing, architectural decoration, electronic products and other fields. However, the surface treatment of aluminum alloy is crucial to improving its performance, enhancing its aesthetics and extending its service life. This article will introduce in detail the common surface treatment processes for aluminum alloys, including several main methods such as sandblasting, polishing, wire drawing, high-gloss cutting, anodizing, and spraying.

Sandblasting

The sandblasting process uses a high-speed sand flow to impact the surface of the aluminum alloy to achieve the purpose of cleaning and increasing the surface roughness. Sandblasting can remove oil stains, oxide layers and other impurities on the surface of the aluminum alloy, providing a good adhesion foundation for subsequent surface treatments such as spraying and electroplating. The surface after sandblasting presents a uniform and fine roughness, which is conducive to the combination of the coating and the substrate. In addition, sandblasting can also be used to create specific surface textures to increase the aesthetics and texture of the product.

1. Polishing

Polishing is a common process in the surface treatment of aluminum alloys. It removes uneven parts of the surface through mechanical, chemical or electrolytic methods to make it smooth as a mirror. There are many types of polishing processes, including mechanical polishing, chemical polishing, electrolytic polishing, ultrasonic polishing, fluid polishing and magnetic grinding polishing. In aluminum alloy processing, mechanical polishing and electrolytic polishing are the most widely used. Mechanical polishing mainly uses polishing wheels and polishing paste to rub the surface, while electrolytic polishing removes microscopic surface unevenness through electrolysis. The polished aluminum alloy surface has extremely high gloss and flatness, and is often used in high-end electronic products, car shells and other parts that require extremely high appearance quality.

2. Wire drawing

The wire drawing process is to form regular lines on the surface of aluminum alloy by grinding to achieve a decorative effect. Wire drawing can not only enhance the beauty of the product, but also cover up some minor surface defects. Depending on the grinding tools and processes, the wire drawing effect can be divided into straight lines, random lines, spiral lines and other types. The aluminum alloy surface after wire drawing has a rich texture and is often used in building decoration materials, electronic product shells and other fields.

3. High light cutting

High light cutting is to use high-precision CNC machining equipment to cut the surface of aluminum alloy to form a local highlight area. This process is often used on the metal shells of electronic products such as mobile phones and tablets. By cutting out highlight chamfers or highlight edges, the overall texture and grade of the product are improved. High-gloss cutting requires high processing precision, and the cutting parameters need to be strictly controlled to ensure that the surface after cutting is flat and smooth, without burrs and scratches.

IV. Anodizing

Anodizing is a chemical treatment method that forms an aluminum oxide film on the surface of aluminum alloy through electrolysis. The anodized film has the characteristics of high hardness, good wear resistance, and strong corrosion resistance, which can effectively protect the aluminum alloy substrate from erosion by the external environment. At the same time, the porous structure of the anodized film gives it good adsorption, which can adsorb various pigments and dyes to form a colorful surface color. Anodizing not only improves the durability of aluminum alloy, but also gives it rich decorativeness. It is widely used in building curtain walls, automotive parts, electronic product housings and other fields.

V. Spraying

Spraying is a process method for evenly applying paint on the surface of aluminum alloy. Spraying can not only protect the surface of aluminum alloy from corrosion and wear, but also give it rich colors and textures. Spraying processes include powder spraying, electrophoretic spraying, fluorocarbon spraying and other types. Powder spraying uses the principle of electrostatic adsorption to evenly apply powder coating on the surface of aluminum alloy, and then forms a solid coating after high temperature curing. Electrophoretic spraying uses the electric field to deposit coating particles on the surface of aluminum alloy to form a coating. Fluorocarbon spraying uses polyvinylidene fluoride as the base material and adds metal powder to synthesize, which has excellent weather resistance and corrosion resistance. The surface of aluminum alloy after spraying is bright in color and high in gloss, and is widely used in architectural decoration, automotive parts, outdoor facilities and other fields.

6. Electroplating

Although anodizing is a common surface treatment method for aluminum alloys, electroplating also has unique advantages in certain specific occasions. Electroplating is the process of plating a layer of metal or alloy on the surface of aluminum alloy using the principle of electrolysis. The electroplating layer can improve the corrosion resistance, hardness and decorativeness of aluminum alloy. Common electroplating processes include chrome plating, zinc plating, nickel plating, etc. Electroplating treatment requires a reasonable formulation of the electroplating solution and precise control of the electroplating parameters to ensure the quality of the coating. However, due to the high reactivity between aluminum alloy and electroplating solution, special pretreatment such as chemical oxidation and chemical plating is usually required before electroplating to improve the adhesion and uniformity of the electroplating layer.

VII. Chemical oxidation

Chemical oxidation is a traditional method for aluminum alloy surface treatment. It forms a thin oxide film on the surface by reacting with an oxidant in an acidic or alkaline solution. The chemical oxide film is thin, about 0.5 to 4 microns, but it is porous and soft, has good adsorption, and can be used as the bottom layer of the organic coating. The chemical oxidation treatment equipment is simple, easy to operate, and has high production efficiency, but the wear resistance and corrosion resistance are slightly worse than those of the anodized film. Chemical oxidation can be divided into two categories according to the properties of the solution: alkaline oxidation and acidic oxidation. According to the properties of the film layer, it can be divided into oxide film, phosphate film, chromate film, etc.

VIII. Electrochemical oxidation (hard anodizing)

Electrochemical oxidation is an advanced method for aluminum alloy surface treatment. It forms a thicker hard anodized film on the surface through electrolysis. The thickness of hard anodized film can reach 60 to 200 microns, with high hardness, good heat resistance and insulation, and excellent corrosion resistance. Hard anodized film can be used not only to protect aluminum alloys from corrosion and wear, but also to manufacture wear-resistant and heat-resistant parts. The electrochemical oxidation treatment equipment is complex and the process parameters are strict, but the surface performance of the treated aluminum alloy is excellent, and it is widely used in high-end fields such as aerospace and automobile manufacturing.

IX. Passivation treatment

Passivation treatment is to form a dense passivation film on the surface of aluminum alloy by chemical or electrochemical methods to improve its corrosion resistance. The passivation film is usually composed of oxides or hydroxides generated by the reaction of metals and oxidants, with a dense structure and good protection. Passivation treatment can not only improve the corrosion resistance of aluminum alloys, but also improve their surface state, making them smoother and more beautiful. Common passivation treatment methods include chromate passivation, nitrate passivation, phosphate passivation, etc.

In summary, there are many surface treatment processes for aluminum alloys, and each process has its unique advantages and scope of application. In practical applications, the appropriate surface treatment process should be selected according to the specific needs of the product and process conditions to achieve the best effect. With the advancement of science and technology and the continuous innovation of technology, the surface treatment technology of aluminum alloy will become more advanced and perfect, providing a more solid guarantee for the wide application of aluminum alloy products.