When China General Nuclear Power Group (CGN) embarked on constructing the nation's largest offshore solar photovoltaic project in Zhaoyuan, Shandong Province, they faced a critical materials challenge. The 400MW installation — located in a high-salinity marine environment (ISO 9223 corrosivity category C5-M) — demanded mounting systems capable of withstanding decades of corrosive exposure while maintaining structural integrity.
This case study examines how our flagship SRPV700D+ZMA system, featuring SOZAMC® proprietary coating (exclusively supplied by Shougang Group), was selected, deployed, and has since validated zero-corrosion performance in this landmark project.
Project Overview
| Parameter | Specification |
|---|---|
| Project Name | CGN Zhaoyuan Offshore Solar PV Project |
| Capacity | 400 MW |
| Location | Zhaoyuan, Shandong Province, China |
| Environment | Offshore/Coastal, High Salinity |
| Mounting System | ZAM Coated Steel (450g/m² coating) |
| Installation Period | 18 months |
The Challenge: Marine Corrosion
Offshore solar installations face unique environmental stresses that rapidly degrade conventional materials:
- High salt spray concentration: Accelerates galvanic corrosion by 5-10× compared to inland environments
- Constant humidity: Maintains electrolytic conditions that promote rust formation
- Temperature fluctuations: Cause thermal expansion stress on mounting connections
- UV exposure: Degrades protective coatings over time
- Mechanical loading: Wind and wave forces create dynamic stress on structures
Key Insight
Traditional hot-dip galvanized steel (HDG) with 275g/m² zinc coating typically shows visible rust within 3-5 years in marine environments, requiring costly maintenance or replacement.
Why ZAM Steel Was Selected
After evaluating multiple material options including aluminum, stainless steel, and various coated steels, the project team selected ZAM-coated steel for several compelling reasons:
1. Superior Corrosion Resistance
ZAM steel's unique coating composition (Zn-6%Al-3%Mg) creates a dense, stable corrosion product layer that provides barrier protection even when the coating is damaged. In salt spray testing (ASTM B117), ZAM 450g/m² outperforms HDG 600g/m² by a factor of 3-4×.
2. Self-Healing Properties
The magnesium content in ZAM coating enables self-healing of minor scratches and cut edges. When exposed to moisture, the coating forms zinc hydroxide and zinc carbonate that seal damaged areas, preventing under-film corrosion.
3. Cost Efficiency
Compared to aluminum mounting systems, ZAM steel offers:
- 40% lower material cost per installed watt
- Superior structural strength (3× higher yield strength than 6061-T6 aluminum)
- Better compatibility with standard installation tools and practices
4. Proven Track Record
ZAM steel had already demonstrated 15+ years of successful performance in Japanese coastal solar installations, providing confidence for this large-scale deployment.
Technical Specifications
The project deployed our flagship SRPV700D+ZMA system, featuring SOZAMC® proprietary coating — exclusively supplied by Shougang Group, combining 700 MPa ultra-high-strength steel with advanced Zn-Al-Mg alloy coating technology.
| Property | SRPV700D+ZMA (SOZAMC®) | HDG 275g/m² (Conventional) |
|---|---|---|
| Product Model | SRPV700D+ZMA | Standard HDG |
| Coating Brand | SOZAMC® (Shougang exclusive) | Pure zinc |
| Coating Composition | Zn-Al-Mg alloy | 99% Zn |
| Salt Spray Resistance (ISO 9227:2017) | >5,000 hours — SGS certified | ~800 hours to red rust |
| Corrosivity Class | C4–C5 (high-marine) | ≤C3 |
| Expected Service Life | 30 years no red rust / 35 years no perforation (Shougang official warranty) | 10–15 years (marine) |
| Yield Strength | 700 MPa | 235 MPa |
Logistics and Installation
The project required careful coordination of material supply and installation:
Material Supply Chain
- Total steel volume: 12,000 tonnes of ZAM-coated steel products
- Delivery schedule: Phased delivery over 12 months to match installation progress
- Quality control: 100% coating thickness inspection, random salt spray testing
- Storage: Indoor warehousing with controlled humidity to prevent pre-installation corrosion
Installation Best Practices
Several key practices were implemented to ensure optimal performance:
- Edge protection: All cut edges were treated with zinc-rich touch-up paint
- Galvanic isolation: Stainless steel fasteners used to prevent dissimilar metal corrosion
- Drainage design: Mounting structures designed to prevent water pooling
- Grounding: Proper electrical grounding to prevent stray current corrosion
Performance Results
After 24+ months of operation in the high-salt marine environment at Zhaoyuan, inspection data shows:
Performance Summary — Zero Corrosion Verified
Zero structural failures. Zero coating degradation visible to naked eye. After 3+ years of real offshore operation, SRPV700D+ZMA (SOZAMC®) mounting structures show no red rust, no structural issues — confirming real-world performance consistent with 5,000+ hour salt spray test results (SGS certified, ISO 9227:2017). 99.7% module retention rate, with only 3 modules requiring repositioning due to installation tolerance, not material issues.
| Metric | Result |
|---|---|
| Modules Installed | 1,200,000+ |
| Annual Energy Output | ~550 GWh |
| COReduction | ~450,000 tonnes/year |
| Maintenance Requirements | Minimal (routine cleaning only) |
Key Lessons for Future Projects
- Material selection is critical: The upfront cost premium for ZAM steel (15-20% vs HDG) is quickly offset by eliminated replacement costs and reduced maintenance.
- Coating thickness matters: For marine environments, 450g/m² minimum is recommended. Thinner coatings may not provide adequate long-term protection.
- Installation quality is paramount: Even the best materials can fail if installation practices create corrosion initiation points.
- Design for the environment: Structural designs should account for thermal expansion, drainage, and wind loading specific to coastal conditions.
Conclusion
The CGN Zhaoyuan project demonstrates that SRPV700D+ZMA (SOZAMC®) mounting systems are a proven, cost-effective solution for large-scale offshore solar installations. With Shougang's official 30-year no red rust / 35-year no perforation warranty, SGS-certified salt spray performance exceeding 5,000 hours (ISO 9227:2017), and 3+ years of verified zero-corrosion field performance, these systems deliver 30+ years of maintenance-free service even in the harshest marine environments.
For EPC contractors and project developers planning similar installations, the key is partnering with experienced suppliers who understand the unique challenges of marine environments and can provide comprehensive technical support from design through commissioning.
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Contact Our EngineersFrequently Asked Questions: Offshore Solar Projects
Why was ZAM steel selected for the CGN Zhaoyuan offshore project?
The coastal Shandong marine environment demands extreme corrosion resistance. CGN selected ZAM steel for its 3–10× longer service life vs HDG in salt spray, and its self-healing coating that protects cut edges and bolt holes—significantly reducing 25-year maintenance costs.
What is the scale of the CGN Zhaoyuan 400MW project?
The CGN Zhaoyuan project is a 400MW offshore photovoltaic installation—the first large-scale fixed offshore PV project in China. Qingdao Develop Group supplied all ZAM steel mounting structures, validating our large-scale offshore supply and technical capability.
What performance data is observed after 3+ years of operation?
After 3+ years in the high-salt marine environment, ZAM mounting structures show no red rust, no structural issues, and minimal coating degradation—confirming real-world performance consistent with 5,000+ hour salt spray test results.
Can mounting systems be customized for project-specific offshore conditions?
Yes. We customize section dimensions, pile depths, and fastener specifications for site wind loads, wave action, and corrosion zones. Full structural calculations and material certificates are provided for project approval documents.