The anti-oxidation treatment process for aluminum alloy storage hangers requires a multi-step synergistic effect to form a dense protective layer on the surface, isolating it from air, moisture, and corrosive media, thereby extending its service life. Its core process encompasses four main stages: pretreatment, oxide film formation, post-treatment, and quality inspection. Each step plays a crucial role in the final anti-corrosion effect.
Pretreatment is the foundation of anti-oxidation treatment, aiming to thoroughly remove oil, oxides, and impurities from the aluminum alloy surface. First, an acid etching process is used, dissolving the surface aluminum oxide layer with a weak acid solution while removing residual cutting fluid, rust-preventive oil, and other organic matter from metal processing. This is followed by alkaline etching, using an alkaline solution to neutralize acid residue and further remove microparticles, resulting in a uniform metallic luster on the substrate surface. Finally, a degreasing process thoroughly removes grease with surfactants or organic solvents, ensuring uniform adhesion of the subsequent oxide film. For example, one factory, when treating storage hangers, first immerses them in a 5% sulfuric acid solution for 3 minutes, then transfers them to a 2% sodium hydroxide solution for 2 minutes, and finally uses an ultrasonic cleaner to remove residual stains.
Oxide film formation is a core step in corrosion prevention, and the most widely used method in industry is anodizing. This method uses an aluminum alloy as the anode, placing it in a sulfuric acid or chromic acid electrolyte. When a direct current is applied, an electrochemical reaction occurs on the aluminum surface, generating an aluminum oxide (Al₂O₃) film of controllable thickness. This film consists of a dense barrier layer and a columnar porous layer. The barrier layer is directly bonded to the substrate, effectively preventing the penetration of corrosive media; the porous layer can be transformed into a dense structure through subsequent sealing treatment. For example, sulfuric acid anodizing can be operated at room temperature, producing an oxide film thickness of 10-20 micrometers with high hardness and wear resistance, suitable for products like storage hangers that need to withstand certain loads.
Post-treatment is crucial for improving the performance of the oxide film. After the oxide film is formed, its porous structure easily adsorbs dust, moisture, and corrosive substances; therefore, sealing treatment is necessary to close the pores. In industrial applications, hot water sealing or cold sealing processes are commonly used. Hot water sealing involves immersing the hook in hot water at 80-100℃, causing the alumina in the oxide film to hydrate and form boehmite (AlO(OH)), thus filling the pores. Cold sealing uses a metal salt solution such as nickel acetate, which forms an insoluble compound in the pores through a chemical precipitation reaction. Furthermore, to enhance the decorative appearance of the hook, dyeing or electrophoretic coating can be applied. Dyeing uses chemical or physical methods to allow dye molecules to penetrate the pores of the oxide film, creating a uniform color. Electrophoretic coating deposits an organic coating layer on the hook surface, further isolating it from corrosive media.
Quality inspection is the final checkpoint to ensure the effectiveness of the anti-oxidation treatment. Inspection mainly includes film thickness, corrosion resistance, and adhesion. The film thickness can be measured using an eddy current thickness gauge or metallographic microscope, generally requiring a thickness of 10 micrometers or more. Corrosion resistance is tested using a salt spray test, placing the hook in a 35°C, 5% sodium chloride solution spray environment and observing the time it takes for corrosion spots to appear on the surface. High-quality oxide films must pass a salt spray test for more than 48 hours. Adhesion is tested using a cross-cut test or a bending test to ensure a strong bond between the film and the substrate, with no peeling.
From pretreatment to quality inspection, the anti-oxidation treatment process for aluminum alloy storage hangers is a precisely controlled system engineering project. The technical parameters of each step must be strictly controlled. For example, excessive acid etching time can lead to over-corrosion of the substrate, unstable oxidation voltage can affect the uniformity of the film thickness, and insufficient sealing temperature cannot completely seal the pores. By optimizing process parameters, the corrosion resistance of the hooks can be significantly improved, allowing them to be used for a long time in harsh environments such as humidity and salt spray without rusting, meeting the storage needs of home and industrial scenarios.
