Anodic oxidation treatment of daily industrial products
Anodizing of daily industrial products is a key process for improving the performance and appearance of aluminum and aluminum alloy products. It is widely used in kitchenware, furniture, electronic product casings and other fields. This process uses aluminum products as anodes, places them in electrolytes such as sulfuric acid and oxalic acid, applies direct current to induce an electrolytic reaction, and forms a dense aluminum oxide film on the surface. Compared with the natural oxide film, the thickness of the anodized film can reach 5-20μm, the hardness is increased by 3-5 times, and it has a porous structure, which can be dyed to give the product a rich color. For example, after the common aluminum alloy frying pan is hard anodized, the surface hardness reaches HV300 or above, the scratch resistance is significantly improved, and it is not easy to be scratched during use. At the same time, it avoids direct contact between food and the aluminum substrate, meeting food safety standards.
Anodizing can significantly enhance the corrosion resistance of daily industrial products, making them adaptable to humid and oily household environments. Untreated aluminum products easily form a loose oxide layer in humid air, causing the surface to darken and rust. The anodized film acts as a physical barrier, effectively isolating water, oxygen, and corrosive substances. Experimental data shows that aluminum alloy samples anodized with sulfuric acid can remain rust-free for 500 hours in a neutral salt spray test, while untreated samples show obvious oxidation spots after only 24 hours. In kitchen environments, anodized sinks, faucets, and other products can resist corrosion from the acid and alkali components in detergents, extending their service life to 8-10 years, far longer than the 3-5 years of ordinary aluminum products. In addition, the insulating properties of the oxide film also prevent the risk of leakage in the anodized aluminum alloy lamp housing, improving safety in use.
Anodizing provides a variety of decorative effects for everyday industrial products, satisfying consumers’ personalized demands for product appearance. The porous structure of the oxide film has a strong adsorption capacity and can be dyed with organic dyes and inorganic pigments to create dozens of colors, including gold, bronze, and black, with uniform color and strong light resistance. For example, high-end aluminum alloy door and window profiles are anodized with oxalic acid and then dyed. The resulting champagne-colored coating has a color difference ΔE value of less than 2 after 1000 hours of xenon lamp aging testing, essentially maintaining its original color. For more demanding electronic product casings, a sealing treatment can also be used to create a mirror-like surface effect. For example, the aluminum alloy middle frame of a smartphone, after anodizing and sealing, retains the metallic texture while being fingerprint-resistant and easy to clean, leaving little mark after touch.
Different types of anodizing processes are suitable for different needs of daily industrial products, and optimizing process parameters is key to ensuring effective treatment. Sulfuric acid anodizing is widely used in consumer goods such as kitchenware and furniture due to its low cost and ease of operation. Typical process parameters are: sulfuric acid concentration of 15%-20%, temperature of 18-22°C, current density of 1-2A/dm², and treatment time of 30-60 minutes, resulting in a transparent or light gray oxide film. Oxalic acid anodizing is suitable for products requiring a more decorative finish, such as lamps and handicrafts. The resulting oxide film is milky white with a high gloss. Treatment requires an oxalic acid concentration of 3%-5% and a temperature of 30-40°C, resulting in slightly higher costs than the sulfuric acid method. Hard anodizing is primarily used for products requiring high wear resistance, such as tools and sports equipment. By increasing the voltage (20-40V) and lowering the temperature (0-5°C), a hard, brittle oxide film with a thickness of 10-50μm and a hardness exceeding HV400 is formed.
Anodizing in the production of daily industrial products requires a balance between performance, cost, and environmental requirements, driving continuous process optimization. Traditional sulfuric acid anodizing produces wastewater containing aluminum ions, which is costly to treat. In recent years, environmentally friendly processes have been increasingly popular. For example, using a low-concentration sulfuric acid electrolyte (5%-10%) combined with membrane separation technology can reduce wastewater emissions by over 60%. Chromium-free sealing processes have replaced traditional chromate sealing, avoiding hexavalent chromium contamination while maintaining sealing quality. A tableware factory using nickel salt sealing achieved corrosion resistance comparable to that of chromate sealing. Furthermore, increasing automation in the process, through robotic loading and unloading and online inspection of film thickness and color difference, has increased product qualification rates from 85% to 98%, reducing production costs. As consumer demand for product quality increases, anodizing will be applied to more daily industrial products, becoming a key means of increasing product value.
