Application examples of chemical oxidation film on aluminum and aluminum alloys
Chemical oxidation coatings on aluminum and aluminum alloys are widely used in architectural decoration due to their ease of application and low cost. In the surface treatment of aluminum alloy doors, windows, curtain walls, and other building components, chemical oxidation coatings provide basic corrosion protection while also laying a good foundation for subsequent coloring and painting. For example, a building curtain wall project used 6063 aluminum alloy profiles. After chemical oxidation with a phosphate-chromate chemical oxidation treatment, an oxide film approximately 1-2μm thick was formed. This film not only provides excellent atmospheric corrosion resistance but also forms a strong bond with fluorocarbon paint. Practical data shows that after five years of use in coastal environments with high humidity and salt content, aluminum alloy curtain walls treated with this treatment show no visible rust or coating peeling, far superior to untreated aluminum alloy components (which typically rust after one to two years). Furthermore, chemical oxidation coatings can be dyed to achieve different colors, meeting the demand for diverse architectural colors. For example, on the aluminum alloy exterior decorative panels of commercial buildings, chemical oxidation followed by dyeing creates attractive and weather-resistant decorative effects such as gold and bronze.
In the electronics and electrical industry, the insulating properties and excellent adhesion of chemical oxide films on aluminum and aluminum alloys make them an ideal surface treatment. In the production of aluminum alloy heat sinks, electronic housings, and other components, chemical oxide films effectively isolate current, preventing short circuits between components while also protecting the aluminum alloy substrate from corrosion by moisture and contaminants. For example, an aluminum alloy heat sink produced by an electronic equipment manufacturer uses a sulfuric acid-chromic anhydride chemical oxidation treatment. The resulting oxide film has a breakdown voltage exceeding 300V, meeting the heat sink’s insulation requirements. Furthermore, the oxide film exhibits a strong bond with the heat dissipation coating. After 100 cycles of thermal cycling (-40°C to 85°C), the coating remained intact, ensuring stable heat dissipation performance. In the treatment of small electronic components such as aluminum alloy connectors, the thin and uniform nature of the chemical oxide film (thickness 0.5-1μm) does not affect component assembly precision while providing essential corrosion protection, extending the connector’s service life in humid environments by more than double its original value.
In the automotive industry, chemical oxidation coatings on aluminum and aluminum alloys are commonly used as surface treatments for non-load-bearing, low-stress components to improve their corrosion resistance and paintability. For example, the aluminum alloy oil pan in an automobile engine, after chemical oxidation treatment, forms a conversion film on its surface. This film effectively prevents corrosion from engine oil and coolant, while also enhancing the adhesion of subsequent oil-resistant coatings. Tests at an automobile manufacturer showed that after a 500-hour hot oil immersion test, the chemically oxidized oil pan showed no signs of corrosion, while untreated oil pans exhibited significant pitting. Furthermore, chemical oxidation coatings used as pre-coating layers on aluminum alloy trim strips, door handles, and other automotive components ensure uniformity and durability. After 1,000 hours of UV aging, the coating’s gloss retention remained above 80%, significantly higher than untreated components, which only maintained a gloss retention of approximately 50%.
In the consumer goods and light industrial sectors, the application of chemical oxidation films on aluminum and aluminum alloys has effectively improved the appearance, quality, and service life of products. For example, after chemical oxidation treatment, the oxide film formed on the surface of aluminum alloy kitchenware (such as pots and kettles) possesses certain corrosion and wear resistance, preventing the corrosion of the aluminum alloy by food residue and detergents while also preventing the precipitation of aluminum ions, thus meeting food safety requirements. Tests conducted by a kitchenware manufacturer showed that after one year of continuous use, the surface of chemically oxidized aluminum alloy pots remained smooth, free of visible scratches and corrosion spots, while untreated aluminum alloy pots showed severe oxidative discoloration and localized corrosion. Chemical oxidation films can be dyed onto aluminum alloy toys, stationery, and other products to achieve rich colors with strong color adhesion, and they remain colorfast even after repeated friction tests, enhancing the product’s market competitiveness.
Chemical oxidation films applied to aluminum and aluminum alloys also have applications on non-critical components in the aerospace industry, primarily for temporary protection and primer pretreatment. For example, during the storage and transportation of aluminum alloy parts, the oxide film formed through chemical oxidation treatment can provide short-term corrosion protection, preventing rust from developing during storage. An airline’s experience has shown that chemically oxidized aluminum alloy conduits remained rust-free after six months of storage, while untreated conduits developed oxidation spots after just two months. On some non-load-bearing aluminum alloy interior trim parts, chemical oxidation films serve as a primer pretreatment layer, improving primer adhesion and ensuring long-term use in the dry, clean environment of the aircraft cabin without coating detachment. Furthermore, the rapid nature of chemical oxidation treatment (typically taking 5-15 minutes) makes it crucial for emergency repairs of aviation parts, rapidly restoring the surface properties and ensuring the normal operation of the aircraft.
