From Extruded Profile to Finished Product
Aluminum extrusion produces near-net-shape profiles efficiently, but the extruded profile is only the starting point. Post-processing transforms raw extrusions into functional, durable, and aesthetically finished components. This guide covers the complete chain: surface treatment, finishing, machining, and assembly.
Surface Preparation
Degreasing and Cleaning
- Alkaline cleaning: pH 11-13, 50-70°C, removes drawing lubricants and die release agents
- Solvent cleaning: IPA or aluminum-safe solvents for spot cleaning
- Ultrasonic cleaning: For complex profiles with internal channels
Etching and Deoxidation
- Chemical etching: NaOH at 40-80 g/L, 50-70°C, dissolves 3-10 µm for uniform matte surface
- Bright dipping: Phosphoric-nitric acid for reflective surface before bright anodizing
- Deoxidation: Removes alloy residue (smut) using nitric acid or proprietary solutions
Anodizing: The Premier Aluminum Finish
Anodizing converts the aluminum surface into dense aluminum oxide (Al₂O₃). Unlike coatings, the anodic layer is integral to the metal — it cannot peel or flake.
Types of Anodizing
- Type I (Chromic Acid): 0.5-5 µm, aerospace use, declining due to environmental restrictions
- Type II (Sulfuric Acid): 5-25 µm, most common for architectural and consumer products
- Type III (Hard Anodizing): 25-150 µm, up to 500 HV hardness, industrial applications
Architectural Anodizing Classes (AAMA)
| Class | Min. Thickness | Environment | Application |
|---|---|---|---|
| AA-C10 | 10 µm | Mild inland | Interior trim |
| AA-C15 | 15 µm | Normal architectural | Window frames |
| AA-C20 | 20 µm | Severe marine/industrial | Coastal curtain walls |
| AA-C25 | 25 µm | Extreme environments | Marine hardware |
Color Options
- Natural (clear): Preserves metallic silver appearance
- Integral colors: Bronze, black, gold via electrolytic coloring (UV-stable)
- Dye colors: Full spectrum but limited UV stability
- Two-step electrolytic: Tin/cobalt salts for UV-stable bronze-to-black
Powder Coating
Electrostatic dry powder cured at 160-200°C forming a polymer film.
Powder Types
- Polyester: Standard architectural, cost-effective
- Super-durable polyester: Enhanced UV for premium architecture
- Fluoropolymer (PVDF): 20+ year warranty, iconic buildings
- Epoxy: Excellent chemical resistance, poor UV, for interiors
Pretreatment
- Alkaline clean → Rinse → Etch → Rinse → Deoxidize → Rinse
- Conversion coating: Chrome-free (zirconium/titanium) increasingly mandated
Mechanical Post-Processing
CNC Machining
- Drilling and tapping for fastener connections
- Milling for slots, pockets, complex contours
- Precision saw cutting (±0.1mm tolerance)
- Chamfering and deburring for assembly fit
Bending and Forming
- Rotary draw bending: Tight-radius curves for trim and handrails
- Roll bending: Large-radius arcs for curtain wall framing
- Stretch forming: Compound curves for automotive and aerospace
Assembly Operations
Thermal Break Assembly
Polyamide strip insertion creating thermally separated inner/outer aluminum sections for window and door systems.
Hardware Installation
- Fasteners, clips, brackets, connectors
- Gaskets and weather seals (EPDM, silicone, TPE)
- Structural adhesives for bonded assemblies
2026 Trends
- Chrome-free conversion coatings becoming standard in EU
- Digital color matching with spectrophotometers
- Robotic powder application for uniform coverage
- Laser marking and QR codes for traceability
- Integrated ERP/MES tracking each profile
CoreMetal Steel: Aluminum Extrusion Partner
We supply 6061, 6063, 6005, 6082 alloys with mill finish, anodized, or powder-coated. CNC machining, custom lengths, full documentation.
Contact: Tracy | tracy@coremetalsteel.com | +86 18291910632
Conclusion
Aluminum extrusion post-processing transforms raw profiles into market-ready products. Selecting the right chain ensures aesthetic and performance requirements. Visit CoreMetal Steel Blog for more.