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Author: Site Editor Publish Time: 2025-06-10 Origin: Site
Wind and snow loads: High-magnitude dynamic forces, especially in extreme weather regions.
Thermal expansion/contraction: Repeated stress from temperature fluctuations.
Environmental exposure: Moisture, salt (coastal areas), industrial pollutants, or UV radiation, all of which impact corrosion resistance.
Strength: Tensile strength ≥ 800 MPa, yield strength ≥ 640 MPa (80% of tensile strength).
Applications:
Suitable for most standard solar mounting systems in moderate climates (non-coastal, low humidity).
Commonly used in frame-to-frame connections, rail-to-post joints, and grounding components.
Corrosion Resistance:
Requires surface treatment (e.g., hot-dip galvanizing, zinc plating) to prevent rust. Galvanized coatings offer ~50–100 μm thickness, providing 10–20 years of corrosion protection in non-aggressive environments.
Advantages: High strength-to-cost ratio; widely available and compliant with standards like ISO 898-1.
Limitations: Poor resistance in high-corrosion environments (e.g., coastal zones, industrial areas) without frequent maintenance.
Strength: Tensile strength ≥ 1,000 MPa, yield strength ≥ 900 MPa (90% of tensile strength).
Applications:
Critical load-bearing joints in large-scale solar farms, high-wind regions (e.g., ≥130 km/h wind speeds), or snow-prone areas requiring extra structural rigidity.
Used in 地脚螺栓 (foundation anchor bolts) or heavy-duty frame connections.
Corrosion Resistance:
Same as 8.8 grade; requires robust surface treatments (e.g., sherardizing, dacromet coating for 1,000+ hours of salt spray resistance).
Advantages: Higher fatigue resistance for dynamic loads; suitable for engineered designs requiring strict compliance with structural codes (e.g., IBC, Eurocode 3).
Limitations: Higher cost than 8.8 grade; still vulnerable to corrosion in harsh environments.
Strength: Typically rated as A2-70 (tensile strength ≥ 700 MPa), lower than high-strength carbon steel.
Applications:
Ideal for coastal areas, high-humidity regions, or installations near swimming pools (chlorine exposure).
Used in non-critical connections (e.g., module clamps, cable tray brackets) where corrosion resistance is prioritized over maximum strength.
Corrosion Resistance:
Naturally resistant to rust due to chromium-nickel alloy (18% Cr, 8% Ni). A2-70 bolts offer ≥500 hours of salt spray resistance per ASTM B117.
Advantages: Maintenance-free; compatible with aluminum or stainless steel mounts to avoid galvanic corrosion.
Limitations: Lower tensile strength; not suitable for heavy-load applications.
Strength: A4-80 grade offers tensile strength ≥ 800 MPa, matching 8.8 carbon steel.
Applications:
Extreme environments (e.g., offshore solar farms, industrial sites with acid rain or chemical exposure).
High-stress connections where both strength and corrosion resistance are critical (e.g., hinge points in tracking systems).
Corrosion Resistance:
Contains molybdenum (2–3%), enhancing resistance to pitting and crevice corrosion. Suitable for marine environments (≤50 km from coastline).
Advantages: Balances high strength and superior durability; meets stringent standards like ISO 3506-1 for marine applications.
Limitations: Highest cost among options; requires careful torque control to avoid galling during installation.
| Factor | 8.8 Carbon Steel | 10.9 Carbon Steel | A2 Stainless Steel | A4 Stainless Steel |
|---|---|---|---|---|
| Tensile Strength | 800 MPa | 1,000 MPa | 700 MPa (A2-70) | 800 MPa (A4-80) |
| Corrosion Resistance | Moderate (with coating) | High (with advanced coating) | Excellent | Superior (marine-grade) |
| Ideal Environment | Inland, low-humidity | High-wind, heavy-load | Coastal, humid | Offshore, industrial |
| Cost | Low | Medium | Medium-High | High |
| Typical Uses | Frame connections | Foundation anchors | Module clamps | Tracking system hinges |
Standard Installations (Inland, Low Corrosion):
Use 8.8 grade hot-dip galvanized carbon steel bolts for main structural connections. Ensure coatings meet ISO 1461 for ≥80 μm thickness.
High-Wind/Snow Regions:
Specify 10.9 grade bolts with dacromet or sherardized coatings for critical joints. Verify compliance with AS/NZS 1170 or local building codes.
Coastal/High-Humidity Areas:
Prioritize A2-70 stainless steel bolts for all exposed components. For heavy loads, upgrade to A4-80 stainless steel.
Galvanic Corrosion Prevention:
Avoid mixing carbon steel with aluminum mounts. Use stainless steel or zinc-plated steel to prevent electrochemical reactions.
Maintenance Considerations:
Carbon steel bolts in corrosive environments require periodic inspection for rust; stainless steel reduces long-term maintenance costs.
Ensure bolts meet international standards:
Carbon steel: ISO 898-1 (property classes 8.8, 10.9).
Stainless steel: ISO 3506-1 (A2, A4 property classes).
For solar-specific applications, reference guidelines like IEC 62305-3 (lightning protection) and UL 2703 (mounting systems).
8.8 carbon steel is the cost-effective choice for most inland projects with moderate loads.
10.9 carbon steel is essential for high-stress environments, paired with advanced anti-corrosion coatings.
A2/A4 stainless steel is non-negotiable in corrosive settings, offering unmatched durability at higher costs.
