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The long-term performance of solar mounting structures hinges on material durability, particularly corrosion and UV resistance. Here’s a technical analysis of mainstream materials:
Corrosion Resistance:
Forms a self-protecting oxide layer (Al₂O₃) when exposed to oxygen, preventing further oxidation.
Ideal for coastal/industrial zones (salt, humidity) due to pitting resistance equivalence number (PREN) > 10.
Vulnerable to galvanic corrosion if paired with carbon steel (requires insulating washers).
UV Resistance:
Inorganic composition ensures zero UV degradation.
Surface anodization (e.g., MIL-A-8625 Type II) enhances reflectivity and wear resistance.
Limitations:
Alkaline soils (pH > 9) or acid rain accelerate corrosion.
Lower yield strength (≥240 MPa) vs. steel necessitates bulkier profiles.
Corrosion Resistance:
Zinc coating (typically 85–100 μm per ASTM A123) acts as a sacrificial anode.
Protects base steel via electrochemical reaction, even if scratched.
Lifespan: 25–50 years in C3/C4 environments (ISO 12944).
UV Resistance:
Zinc layer blocks UV radiation; minor chalkiness over time doesn’t affect function.
Critical Failure Modes:
White rust: Forms if stored damp pre-installation (prevent with chromate passivation).
Galvanic corrosion: Accelerated when contacting stainless steel or copper.
Superior Corrosion Resistance:
Composition: Zn + 4–11% Al + 2–3% Mg (e.g., Magnelis®/ZAM®).
Self-healing properties: Mg/Zn salts seal scratches and cut edges.
Salt spray resistance: 1,000–1,500 hrs (vs. 500–720 hrs for HDG per ASTM B117).
UV Stability:
Stable intermetallic layer (Zn-Al-Mg oxides) resists UV-induced degradation.
Applications:
Replaces HDG in coastal/offshore solar farms.
Thinner coatings (e.g., 40 μm ZM ≈ 80 μm HDG performance) reduce material use.
| Property | Aluminum Alloy | HDG Steel | ZM-Coated Steel |
|---|---|---|---|
| Corrosion Resistance | Excellent (PREN>10) | Good (85μm coating) | Exceptional (3x HDG) |
| UV Resistance | Perfect | Very Good | Very Good |
| Strength (Yield) | 240–300 MPa | 350–450 MPa | 350–450 MPa |
| Weight | Lightweight | Heavy | Heavy |
| Cost | High | Low | Medium |
| Lifespan (C4 env.) | 30–40 years | 25–35 years | 40–60 years |
Environment:
Coastal/Industrial: Use ZM-coated steel or aluminum with isolation.
Inland/Rural: HDG suffices.
Structural Load:
High wind/snow: Steel’s strength is preferable.
Sustainability:
Aluminum: 95% recyclable; ZM steel: 50% lower CO₂ vs. HDG.
Aluminum: EN AW-6005A (EN 573), Anodizing per EN ISO 10074
HDG Steel: ASTM A123 (≥85μm for structural parts)
ZM Coatings: EN 10346:2015 (ZM310/420 grades)
Mitigate Failures: Avoid mixed-metal connections without dielectric insulation. Specify torque-controlled bolts (e.g., M12 10.9 grade) to prevent crevice corrosion.
Proven Solutions:
Offshore Solar (Netherlands): ZM-coated piles endured North Sea salinity for 10+ years.
Desert Farms (Chile): Anodized aluminum mounts resisted UV/sand abrasion at 2,500m altitude.
Conclusion: Aluminum excels in weight-sensitive/corrosive sites; ZM steel dominates extreme environments. Prioritize third-party validated coatings (e.g., Qualisteel for ZM) to ensure 30-year ROI.
