Ordinary anodizing technology
Conventional anodizing technology is a surface treatment process that generates an oxide film on the metal surface through electrolysis. Its core principle is to use the metal workpiece as the anode, place it in a specific electrolyte, and under the action of an external direct current, cause an oxidation reaction on the metal surface to form an oxide film that is firmly bonded to the substrate. Unlike chemical oxidation, anodizing uses electrical energy to drive the reaction, which can more accurately control the thickness and performance of the oxide film. The resulting oxide film generally has higher hardness, wear resistance, and corrosion resistance. This technology is widely used in the surface treatment of various metal materials, especially in metals such as aluminum, magnesium, copper, and their alloys. It is an important means to improve the surface performance of metals in industrial production.
Conventional anodizing technology uses a wide variety of electrolytes, each of which affects the structure and properties of the oxide film. The most commonly used electrolyte is sulfuric acid, suitable for anodizing aluminum and aluminum alloys. It produces a porous, uniform oxide film, facilitating subsequent dyeing and sealing. Oxalic acid, often used for applications requiring high corrosion resistance, produces a dense but thin oxide film. Chromic acid produces an oxide film with strong adhesion to the substrate, making it suitable for high-end applications such as aerospace. However, due to the high toxicity of chromic acid, its application is limited. Other electrolytes include phosphoric acid and boric acid, each of which is selected based on the metal type and performance requirements.
The conventional anodizing process primarily consists of three stages: pretreatment, anodizing, and post-treatment. Pretreatment is essential for ensuring the quality of the oxide film and includes steps such as degreasing, pickling, and polishing. Degreasing removes grease from the workpiece surface using either an alkaline solution or an organic solvent; pickling removes surface scale and rust, revealing a clean metal surface; and polishing improves surface finish and is suitable for workpieces requiring a high level of aesthetic appeal. During the anodizing stage, the pretreated workpiece serves as the anode, placed in an electrolyte, and supplied with direct current, controlling parameters such as voltage, current density, temperature, and time. Generally, the voltage is between 10-20V, the current density is 1-2A/dm², and the temperature is controlled between 15-25°C. The treatment time is determined by the desired film thickness and is typically 20-60 minutes.
Conventional anodizing techniques produce an oxide film with a unique porous structure, which imparts excellent adsorption properties and allows for dyeing to create a rich variety of colors, satisfying decorative needs. Furthermore, sealing treatments (such as hot water sealing, steam sealing, and salt solution sealing) can fill the pores in the oxide film, further enhancing its corrosion and wear resistance. For example, architectural aluminum profiles that undergo anodizing, dyeing, and sealing not only look beautiful but also withstand harsh outdoor environments, resulting in a service life of decades.
With the advancement of industrial technology, conventional anodizing technology continues to improve and innovate. The development of low-energy, environmentally friendly electrolytes, such as the application of chromium-free anodizing processes, has reduced environmental pollution. The introduction of automated production lines has improved production efficiency and the stability of oxide film quality. Composite anodizing techniques (such as combining anodizing with electroplating and coating) have further expanded its application areas. In the future, conventional anodizing technology will continue to develop towards high efficiency, environmental protection, and functionalization, playing a more important role in the automotive, construction, electronics, aerospace, and other fields.
