3. Classification of anodizing
4. What are the technical inspection standards for anodized products?
5. What are the color types of anodizing?
6. Analysis of the main defects and causes of anodizing
7. Which precision appearance parts are suitable for anodizing process?
8. The choice of anodizing and sandblasting processes
1. What is anodizing?
2. Anodizing process
3. Classification of anodizing
4. What are the technical inspection standards for anodized products?
5. What are the color types of anodizing?
6. Analysis of the main defects and causes of anodizing
7. Which precision appearance parts are suitable for anodizing process?
8. The choice of anodizing and sandblasting processes
Anodizing is a commonly used surface treatment technology through which an oxide film can be formed on the surface of aluminum and its alloys to improve its corrosion resistance, wear resistance and decorative properties. Anodizing is an electrochemical process that causes an oxidation reaction on the surface of aluminum and its alloys through the action of electric current to form a dense oxide film. Specifically, during the anodizing process, aluminum or aluminum alloy serves as the anode and undergoes an oxidation reaction with hydrogen ions in the electrolyte to generate aluminum oxide and water, while releasing electrons. In the cathode reaction, water is reduced to hydrogen gas. As the reaction proceeds, an oxide film gradually forms on the aluminum surface, and its thickness can be adjusted as needed.
Anodizing processing is divided into current types: direct current anodizing and alternating current anodizing. The main reason is that the current method is different.
It is distinguished by the thickness of the oxide film: hard anodizing, the film thickness can reach 50~100 microns, and the surface hardness can reach HV350~HV550; ordinary anodizing, the film thickness is 8~12 microns, and the surface hardness is HV250~HV350.
According to the electrolyte, there are: sulfuric acid, oxalic acid, chromic acid, mixed acid and naturally colored anodizing with sulfo-organic acid as the main solution.
Check whether the surface of the workpiece is clean and whether there are impurities such as oil, dust, oxides, etc.
Use color cards to compare to meet the standards of customer signatures.
Use a roughness tester to detect the roughness of the workpiece surface to ensure that it meets customer requirements.
Use a film thickness tester to measure the thickness of the oxide film to determine whether it meets the standards required by the customer.
Use cross-hatch test or other adhesion test methods to detect the bonding force between the oxide film and the substrate.
Carry out salt spray test or other corrosion tests to evaluate the corrosion resistance of the oxide film.
Use dyeing method, thermal weight loss method, etc. to detect the sealing quality to ensure that the pores of the oxide film are effectively sealed.
These quality testing standards can help ensure the effectiveness of anodizing pre-treatment, thereby improving the quality and performance of the oxide film.
Anodizing is generally based on the function and appearance requirements of the product, and there are several common color standards:
The color of natural color anodizing is mainly silvery white. Natural color anodizing means that after the aluminum alloy is anodized, the color does not change and the original color of the metal is maintained. This treatment method is usually used for 1 series, 5 series or 6 series aluminum alloys. These series of aluminum alloys are suitable for natural anodizing treatment.
Black can be divided into bright black and matte black. Black can not only show the stability of the product, but also enhance the fashion sense of the product, making the product more competitive in the market.
Dyeing with a solution containing gold dye gives the aluminum plate a golden appearance. Bright gold gives people a sense of nobility and luxury, and is widely used in decorative materials, electronic product casings and other fields.
Obtained by adding red dye. Red gives people a warm and energetic feeling and is widely used in auto parts, electronic products, decorative materials and other fields.
dyeing by adding blue dye. The blue anodized aluminum plate is bright in color and has a youthful and energetic visual effect. It is often used in sports equipment, electronic products and other fields.
Obtained by adding purple dye. Purple is a mysterious and aristocratic color, often used in high-end cosmetic packaging, jewelry boxes, etc.
The color can also be customized according to the needs of customers and configured with different dyes to meet various customization needs of customers.
(1) It may be that the composition of the aluminum alloy material is uneven, causing spots to appear after anode.
(2) The pre-treatment degreasing process is not thorough and the ultrasonic cleaning is not clean, which will cause obvious white spots on the film layer, which will affect the subsequent coloring and cause defects.
When the concentration of Sn salt in the electrolytic solution is too low, the coloring speed is slow. When the concentration is higher than 25 g/L, the coloring speed is fast, but it is difficult to master, and color difference often occurs. larger.
The main reason is that the dyeing process is too short, which will cause the product to be light in color and fade.
The anodizing time and current density will directly affect the thickness and quality of the oxidized film.
CNC processed products of aluminum alloy profiles and bars are suitable for anodizing treatment, but aluminum alloy die-casting products are not suitable for anodizing treatment. The main reason is that the density of die-casting products is poor, and the surface of anodized products will form small holes like holes. Affect product appearance.
For aluminum alloy products with the following requirements, the anodizing process is suitable:
For those CNC parts that need to work in harsh environments, such as moisture, corrosive gas or liquid environments, anodizing can significantly improve their surface properties and extend their service life.
Anodizing can not only form a protective oxide film on the surface of the part, but also make the surface of the part show various bright colors through dyeing or coloring processes to meet the aesthetic needs of different customers.
In situations where electrical insulation is required, such as casings of electronic equipment, connectors, etc., anodizing can significantly improve the insulation performance of the parts. Prevent current leakage and ensure the safe operation of equipment.
For the product anodizing process, some products do not require sandblasting, mainly because customers like to retain the surface texture of the product after processing and have a metallic texture. However, in the actual production of precision appearance parts, due to the soft hardness of aluminum, some defects in appearance will inevitably be caused during product processing and logistics. Therefore, sandblasting before oxidation can play the following roles:
Surface sandblasting can remove the oil film and dirt on the aluminum surface. This is because during the anodizing process, if dirt exists on the surface, it will affect the quality of the oxide film and cause problems such as uneven oxide films and bubbles.
Sandblasting will form tiny protrusions and depressions on the aluminum surface, which can increase the contact area between the oxide film and the aluminum surface and improve the adhesion of the oxide film.
Sandblasting can create a frosted effect, making the aluminum surface more uniform and beautiful. This can improve the grade and quality of aluminum.
The size of the sandblasting grains directly affects the surface roughness of the product and plays a decisive role in the appearance of the product. Customers need to choose the size of the sandblasting model according to the appearance requirements of the product. The surface roughness corresponding to the size of the sand grains is as follows:
10-20 mesh: Suitable for heavy cleaning and rust removal, such as pretreatment of structural steel parts with high roughness.
20-40 mesh: Coarse sand with a particle size range of 0.42-1.2mm. It is suitable for removing thick coatings and has high roughness.
40-60 mesh: medium-coarse sand with a particle size range of 0.3-0.45, which can both clean the surface and create a certain roughness.
60-80 mesh: medium sand, particle size range is between 0.15-0.3, suitable for sand blasting of general metal materials, with moderate surface roughness.
80-120 mesh: fine sand with a particle size range of 0.125-0.2mm, which can both clean the surface and maintain a certain roughness.
120-220 mesh: finer sand, particle size range is between 0.07-0.125, suitable for fine sandblasting and surface beautification, lower roughness, general precision appearance parts, such as consumer electronics and other appearance parts are used This sandblasting range.
With the continuous advancement of science and technology and the expansion of application fields, anodizing technology will have wider application prospects. Future development directions include developing efficient and energy-saving anodizing processes, researching new electrolytes and additives, and developing environmentally friendly sealing methods. At the same time, as people's requirements for product appearance and quality continue to increase, the application fields of anodizing will be further expanded.
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