How do aluminum alloy nuts, treated with natural anodizing, maintain long-term corrosion resistance under strong ultraviolet radiation?
Publish Time: 2026-01-31
In ultraviolet (UV) sterilization equipment, every component must withstand long-term exposure to high-intensity UV radiation, high humidity, and even ozone environments. As a critical fastener, the small aluminum alloy nut plays a vital role in sealing, fixing, and structural support. Its natural anodizing treatment not only gives the aluminum nut excellent appearance and hardness but also demonstrates superior corrosion resistance and anti-aging properties under extreme conditions.1. The Essence of Anodized Film: A Dense Alumina BarrierNatural anodizing involves electrolysis to generate an amorphous alumina layer in situ on the surface of high-purity aluminum or aluminum alloys. This film is typically 10–25 micrometers thick, with a dense structure, low porosity, and metallurgical bonding to the substrate, eliminating the risk of peeling. Unlike ordinary coatings, the alumina in aluminum alloy nuts is chemically extremely stable—insoluble in water, resistant to acids and alkalis, oxidation-resistant, and completely inert to ultraviolet light. Even under continuous irradiation in the 254nm UVC band, alumina will not undergo photodegradation, yellowing, or embrittlement, fundamentally avoiding the chalking and cracking problems common to organic coatings.2. No dyes, no sealing agents: Eliminating the risks of UV agingThe key to "natural" anodizing lies in the absence of organic dyes and silicone/nickel salt sealing agents. Traditional colored anodizing relies on dyes to fill micropores, but these organic substances are highly susceptible to photo-oxidation under strong UV irradiation, leading to fading, release of volatile substances, and even contamination of the sterilization chamber. Natural anodizing retains the natural color of aluminum, using only high-temperature hydration or cold sealing to allow the micropores to naturally hydrate, expand, and close. This inorganic sealing method is fully compatible with the UV environment, ensuring that the nut maintains surface integrity after thousands of hours of irradiation, with no harmful leaching, meeting high hygiene standards for medical and drinking water applications.3. High hardness and wear resistance: Ensuring reliability after repeated disassembly and assemblyUV sterilizers often require regular maintenance, lamp replacement, or chamber cleaning, and the nut must withstand repeated tightening and loosening. Natural anodized films achieve a hardness of HV 300–500, significantly higher than the base aluminum, effectively resisting scratches or wear on the mating surfaces caused by wrench slippage. More importantly, the high-hardness surface reduces fretting wear, preventing loosening due to vibration and maintaining the airtightness of the chamber—crucial for disinfection systems relying on negative pressure or ozone circulation.4. Electrochemical Stability: Preventing Dissimilar Metal CorrosionInside the sterilizer, the aluminum alloy nut often comes into contact with stainless steel supports, quartz sleeves, or copper connectors. If surface treatment is inadequate, aluminum-stainless steel galvanometers are prone to electrochemical corrosion in humid environments. Natural anodized films, as excellent insulators, effectively block electron pathways, significantly reducing the risk of galvanometer corrosion. Simultaneously, their uniform coverage ensures no exposed aluminum substrate, further enhancing long-term corrosion resistance in condensate or high-humidity environments.5. Thermal Stability and Low Thermal Expansion MatchingUVC lamps can reach surface temperatures of 80–120°C during operation, and frequent start-stop cycles cause thermal cycling. Although alumina has a higher coefficient of thermal expansion than the aluminum substrate, its thin film and porous structure provide a certain degree of cushioning, resulting in very few cracks in actual use. Furthermore, alumina's good thermal conductivity helps with localized heat dissipation, preventing heat buildup and accelerated aging.The "natural anodizing" of aluminum alloy nuts is not merely a simple surface treatment, but a sophisticated protective solution integrating materials science and environmental engineering. Using an inorganic, dense, and high-hardness alumina film as a shield, it silently protects the structural integrity and internal cleanliness of equipment in harsh environments with strong ultraviolet radiation, high humidity, and ozone. It is this "invisible stability" that makes every sterilization process trustworthy—because true safety begins with the meticulous attention to detail in every screw.
