About Solar Racking FAQ

A: Galvanized solar racking refers to steel support systems for solar panels with a hot-dip galvanized surface treatment. It forms a corrosion-resistant protective layer by coating steel with a zinc layer (thickness ≥85μm), suitable for scenarios requiring high strength but moderate corrosion resistance (e.g., industrial plants, inland projects).

A: 

A: Principle: Steel is immersed in molten zinc to form a composite coating of zinc-iron alloy (Fe-Zn) and pure zinc (Zn). The thickness increases with steel thickness (e.g., ≥85μm for 4mm steel plates).
Advantages:
◇  Electrochemical protection: Zinc layers corrode preferentially to safeguard the steel substrate, and damaged areas self-repair via zinc layer migration.
◇  Longevity: 15–20 years in inland areas, 5–8 times longer than bare steel.
◇  Cost-effectiveness: 30%–50% lower anti-corrosion costs than stainless steel or aluminum alloys.

A: Industrial and commercial projects: Large ground-mounted power stations (≥10MW), warehouse roofs (load-bearing ≥3kN/m²);
High-load environments: Snowy areas (snow load ≥1.5kPa), large-span racks (span >3m);
Inland non-corrosive environments: Temperate regions far from coastlines or acid rain;
Low-cost projects: Scenarios requiring high strength on a limited budget (e.g., agricultural PV greenhouses).

A: Magnetic thickness gauge: Directly measure zinc layer thickness (standard requires ≥85μm, compliant with ISO 1461);
Copper sulfate test: Apply copper sulfate solution and observe discoloration time (≥30 seconds without red rust is qualified);
Destructive testing: Cut samples to observe zinc-iron alloy layers under a microscope (for sampling quality inspection only).

A: Avoid zinc layer damage:
◇  Protect with rubber pads during handling; never bind with steel wire ropes (prone to scratching the zinc layer).
◇  Remove the zinc layer within 20mm of welding points on-site; apply zinc-based primer + anti-rust paint (e.g., cold-spray zinc agent) after welding.
Grounding treatment:
◇  Use 40×4mm galvanized flat steel for grounding (ground resistance ≤4Ω); scrape the zinc layer at bolt connections to ensure conductivity.
◇  Never directly contact aluminum alloy panel frames (risk of electrochemical corrosion); isolate with insulating gaskets.
Fastener selection:
Bolts and nuts must be hot-dip galvanized (grade 8.8 or higher); avoid mixing carbon steel with galvanized steel (accelerates corrosion).

A: Limited application:
Use with caution within 5km of the coastline; zinc layer lifespan shortens to 5–8 years at salt fog concentrations >500mg/m³.
Solutions:
◇  Increase zinc layer thickness to ≥120μm (e.g., ASTM A123 standard).
◇  Apply extra fluorocarbon paint (dry film thickness ≥60μm) for salt fog resistance ≥1,000 hours.
◇  Prioritize 316 stainless steel connectors (bolts, nuts).

A: Snow load: Comply with local building codes (e.g., GB 50009 requires ≥0.5kPa in China, ≥1.5kPa in Northeast China). Design diagonal braces to prevent snow accumulation.
Wind resistance load:
◇  Basic wind pressure ≥0.35kN/m² (wind speed 25m/s), ≥0.6kN/m² in coastal areas (wind speed 35m/s).
◇  Calculate wind vibration coefficients for the windward surface of racks (consider dynamic wind pressure for tall racks); bolt spacing ≤600mm to prevent loosening from vibration.

A: Small-area damage (<10cm²):
◇  Sand the damaged area to a metallic sheen.
◇  Apply cold-spray zinc agent (zinc content ≥95%) with a dry film thickness ≥80μm.
◇  Cover with anti-rust paint (e.g., alkyd enamel).
Large-area damage (>10cm²):
◇  Cut out damaged components and replace with new galvanized parts.
◇  If replacement is impossible, treat as above and add zinc alloy patches via welding.

A: Regular maintenance:
◇  Inspect zinc layer integrity annually, focusing on welded points and bolt holes-prone to corrosion.
◇  Flush sand/dust/bird droppings with neutral detergent (pH 6–8) to prevent long-term residue of acidic substances (e.g., acid rain).
Environmental control:
◇  Apply an anti-corrosion coating every 2 years in industrial pollution zones (e.g., near chemical plants).
◇  Increase ventilation in high-humidity areas (humidity >80%) to avoid condensed water accumulation.

A: Weight matching:
◇  Module weight ≤ rack design load (e.g., 10kg/m² modules require racks to bear ≥50kg/m², including wind/snow loads).
◇  For large modules (e.g., 182mm/210mm wafer modules), reduce rail spacing to ≤1.2m.
Thermal expansion and contraction:
◇  Set expansion joints (gap 5–8mm) for rails >6m to prevent deformation from temperature changes.
◇  Design bolt holes as oblong holes (length direction aligned with thermal expansion direction).

A: Material cost: Galvanized steel is 20%–30% cheaper than aluminum alloy (e.g., Q235B steel ~CNY 5,000/ton, 6061 aluminum alloy ~CNY 18,000/ton).
Installation cost:
◇  Ground-mounted racks: Galvanized racks cost 10%–15% more for hoisting due to heavier weight.
◇  Roof-mounted racks: Ballasted galvanized racks require more weights (cost +5%–8%); hook-mounted installation costs are similar to aluminum alloy.
◇  Comprehensive cost: Galvanized racking is 15%–20% cheaper overall under the same load, suitable for large-scale projects.

A: Hot-dip galvanizing standards:
◇  China GB/T 13912 Metallic Coatings-Hot-Dip Galvanized Coatings on Fabricated Iron and Steel Articles;
◇  USA ASTM A123 Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products.
Structural standards:
◇  China GB 51391 Design Code for Solar Photovoltaic Support Systems;
◇  International ISO 12944-5 Protective Coatings Systems-Protection of Steel Structures.

A: Low-temperature properties of steel:
◇  Q235B steel has an impact energy ≥27J at -20℃ (compliant with GB/T 700), requiring no special treatment in general low-temperature areas (above -30℃).
◇   In extremely cold regions (below -40℃), use Q355ND low-temperature steel (impact energy ≥34J at -40℃) and enhance rack toughness (e.g., rounded corners to reduce stress concentration).