Aluminum plates are widely used in numerous industries due to their lightweight, corrosion resistance, and excellent mechanical properties. However, to enhance their durability, aesthetics, and functional performance, surface treatment of aluminum plate bases is essential.
Aluminum plates, typically composed of alloys such as 1xxx, 3xxx, 5xxx, and 6xxx series, provide a versatile foundation in construction, transportation, aerospace, and electronics. The intrinsic oxide layer on aluminum offers basic protection, but industrial demands necessitate more advanced surface treatments for enhanced performance.
2. Importance of Surface Treatment
Surface treatment improves the surface quality, corrosion resistance, wear resistance, and bonding capability of aluminum plates. It also influences color and reflectivity, making aluminum suitable for decorative and structural applications.
3. Common Surface Treatment Methods
3.1 Anodizing
Process: An electrochemical oxidation technique where the aluminum plate is immersed in an acidic electrolyte, producing a thick, porous oxide layer.
| Parameter | Value |
|---|---|
| Electrolyte type | Sulfuric acid, oxalic acid, or chromic acid |
| Typical oxide thickness | 10 – 25 microns (standard anodizing) |
| Hard anodizing thickness | 50 – 150 microns |
| Operating temperature | 0 – 20 °C |
| Voltage range | 12 – 25 volts |
Features:
Enhanced corrosion strength and wear resistance
Good adhesion for subsequent paint or adhesive
Ability to dye pores for varied colors
Inert and non-conductive surface layer
Applications:
Architectural facades
Electronic device housing
Automotive parts
Cookware and kitchen utensils
3.2 Electroplating
Process: Depositing a thin coating of metals like nickel, chromium, or copper on aluminum to improve surface properties.
| Coating Type | Layer Thickness | Benefits |
|---|---|---|
| Nickel plating | 5 – 25 microns | Enhanced hardness and corrosion resistance |
| Chromium plating | 0.5 – 3 microns | Improved wear resistance and aesthetics |
| Copper plating | 5 – 10 microns | Better solderability and conductivity |
Features:
Increased hardness and scratch resistance
Improved corrosion resistance (when combined with sealing)
Enhanced conductivity for electrical components
Applications:
Electrical connectors
Decorative trim pieces
Precision instruments
3.3 Powder Coating
Process: Applying a dry powder electrostatically on the aluminum plate and then curing at high temperature to form a solid, protective film.
| Parameters | Typical Values |
|---|---|
| Curing temperature | 160 – 210 °C |
| Coating thickness | 50 – 100 microns |
| Types of powders | Epoxy, polyester, hybrid |
Features:
Durable and weather-resistant finish
Wide range of colors and textures
Environmentally friendly with low VOC emissions
Applications:
Outdoor equipment housings
Automotive parts and chassis
Appliances and furniture
3.4 Mechanical Treatments (Polishing and Brushing)
Process: Using abrasive tools or polishing agents to create smooth, reflective, or matte finishes.
| Technique | Outcome |
|---|---|
| Polishing | Mirror-like surface |
| Brushing | Satin, matte texture |
Features:
Improved aesthetics
Enhanced cleanability
Preparation for further coatings or treatments
Applications:
Consumer electronics
Decorative panels
Signage and displays
3.5 Chemical Etching and Passivation
Process: Using acid or alkaline solutions to remove impurities and create specific surface textures or to neutralize chemically active residues after plating.
Features:
Removes surface contaminants and oxides
Enhances adhesion of coatings
Creates matte or textured finishes for special use
Applications:
Pre-treatment in coating production
Fabrication of nameplates, circuit boards
Aerospace and defense components
4. Chemical Composition of Common Aluminum Alloy Plates
| Alloy Series | Main Elements (wt%) | Characteristics |
|---|---|---|
| 1xxx | >99% Aluminum | Excellent corrosion resistance, high thermal & electrical conductivity |
| 3xxx | Mn 1.0 – 1.5 | Good corrosion resistance, moderate strength, excellent weldability |
| 5xxx | Mg 3.0 – 5.0 | High strength, excellent corrosion resistance, heat workability |
| 6xxx | Mg 0.8 – 1.2, Si 0.4 – 0.8 | Medium to high strength, good corrosion resistance, good formability |
