In the manufacturing workshop of smartphone casings, airplane skins, and building curtain walls, a mirror smooth aluminum plate can be transformed into a “smart skin” that is fingerprint resistant, scratch resistant, and even discolored after undergoing mysterious processing. This is the magic of aluminum surface treatment technology – through physical, chemical, or biological means, various functional “molecular armors” are constructed on the surface of aluminum, allowing ordinary metals to radiate extraordinary vitality.
Why is surface treatment necessary?
Although aluminum is known as the “metal that never rusts”, its natural characteristics have three major shortcomings:
Corrosion prone: In humid environments, aluminum reacts with oxygen to form an aluminum oxide protective layer, but acidic or alkaline environments can damage this natural barrier.
Poor wear resistance: Pure aluminum has a hardness of only HV15-20 (steel has HV40-60), and scratches are prone to occur during daily friction.
Aesthetic limitations: The untreated aluminum surface is dull and lacks luster, making it difficult to meet high-end design requirements.
Surface treatment technology is aimed at addressing these issues by forming a functional coating of 0.1-500 μ m on the surface of aluminum, endowing it with characteristics such as corrosion resistance, wear resistance, and decoration. More than 200 million tons of aluminum undergo surface treatment worldwide every year, creating a production value of over 300 billion US dollars.
Full analysis of mainstream surface treatment technologies
Anodizing: Electrolysis magic creates’ armor ‘
Principle: Immerse the aluminum material in sulfuric acid electrolyte and generate a 10-200 μ m alumina ceramic layer on the surface after being electrified.
Technical highlights
Forming a micro scale honeycomb structure with a hardness of up to HV300 (increased by 15 times)
Can be dyed into over 200 colors (such as gradient blue for iPhone).
Salt spray corrosion resistance up to 2000 hours (ordinary aluminum plate only 500 hours).
Application case
Aerospace: Boeing 787 fuselage skin anodized treatment improves UV aging resistance by three times.
Building curtain wall: Alucobond composite panel anodized film thickness of 50 μ m, with a lifespan of over 50 years.
Electroplating: Cross border Integration of Metal Coatings
Principle: By electrochemical deposition, nickel, chromium, tin and other metal layers are covered on the surface of aluminum.
Innovation breakthrough:
Nanoelectroplating: Japan develops ultra-thin coatings with a thickness of only 1 μ m to maintain the advantage of lightweight substrate.
Composite electroplating: Adding diamond particles to the plating solution to increase the hardness to HV1000.
Environmental substitution: Cyanide free electroplating process reduces heavy metal emissions by 90%.
Application scenarios
Automotive components: Tesla battery tray plated with nickel layer, capable of withstanding high temperatures up to 800 ℃.
Electronic products: MacBook shell plated with copper layer, thermal conductivity improved by 40%.
Micro arc oxidation (MAO): an “atomic furnace” for ceramic coatings
Technical principle: Under high voltage electric field, plasma discharge is generated on the surface of aluminum, forming a 10-200 μ m ceramic layer.
Performance advantages:
Wear resistance: The wear rate is as low as 5 × 10 ⁻⁷ mm ³/N · m (1/5 of anodizing).
Insulation performance: breakdown voltage up to 2000V/mm (10 times that of steel).
Biocompatibility: medically certified for use in artificial joint implantation.
Frontier applications:
Medical equipment: Germany B Braun surgical instruments are coated with MAO on the surface, with an antibacterial rate of 99.9%.
Spacecraft insulation: NASA developed Al ₂ O ∝ – TiO ₂ composite ceramic layer, temperature resistant to 2000 ℃.
Chemical conversion film: the “invisible shield” for green manufacturing
Technical features: No need for electricity, generate protective film in room temperature solution.
Typical process:
Chromate conversion: Excellent corrosion resistance, but hexavalent chromium is carcinogenic (banned by the European Union).
Phosphate chromate conversion: a chromium free and environmentally friendly alternative solution, fully applied in Ford’s production line.
Silane treatment: Replacing metal salts with organosilane molecules reduces wastewater treatment costs by 70%.
Disruptive new technological revolution
Nano coating: molecular level precision protection
The “biomimetic lotus leaf effect” coating developed by Harvard University has a contact angle of 160 degree and water droplets automatically roll off BASF nanoceramic coating from Germany, with a thickness of 200nm, can resist sand and gravel impact.
Self healing coating: the “self regeneration” of materials
Kansai Coatings in Japan has developed a microcapsule self-healing system that releases repair agents at scratch sites, allowing for 24-hour restoration.
Hefei Institute of Materials Science and Technology, Chinese Academy of Sciences, has developed a thermally responsive coating that automatically repairs upon exposure to heat.
Intelligent color changing coating: a surface that can ‘think’
Gentex electrochromic glass from Israel, with light transmittance adjusted by voltage (1% -80%)
Merck electronic ink technology from Germany achieves dynamic switching of surface patterns on aluminum plates.
Industry application panorama
Consumer electronics: a showcase of precision craftsmanship
The frame of Huawei Mate series adopts micro arc oxidation+PVD coating, with a thickness of only 0.6mm. The Samsung Galaxy S24 Ultra frame uses diamond-like carbon film (DLC) with a hardness of HV900.
New Energy Vehicles: Balancing Lightweight and Safety
BYD blade battery tray adopts anodizing+epoxy resin coating, flame retardant grade UL94 V-0
The BMW iX chassis armor is coated with ceramicized silane, which reduces weight by 30% and is impact resistant.
Architectural Curtain Wall: Technological Expression of Urban Aesthetics
The exterior walls of the Burj Khalifa in Dubai are coated with fluorocarbon, with a weather resistance of up to 50 years.
The tower crown of Shanghai center Building uses photocatalysis self-cleaning coating to remove dust after rain wash.
Future Trends and Challenges
Green Manufacturing Transformation
Biobased conversion agent: using plant extracts to replace traditional chemicals
Low temperature plasma treatment: energy consumption reduced by 50%, no wastewater discharge.
Multi functional integration
Research and development of superhydrophobic, antibacterial, and conductive three in one coating
Stretchable electronic coating: maintains conductivity even with a stretching rate of 300%.
Intelligent development
Sensor integrated coating: Real time monitoring of material health status.
Light responsive color changing coating: automatically adjusts color depth according to UV intensity.
Post time: Apr-09-2025