The global photovoltaic (PV) industry is growing rapidly, and its installation scenarios are expanding all over the world. This growth trend is putting more stringent performance demands on solar mounting systems. Solar mounting materials not only bear the weight of PV modules, but they also stay exposed to the outdoors for long periods of time. Their durability, corrosion resistance, and cost-effectiveness directly determine the operational stability and service life of the entire PV system. Hot dipped galvanized (HDG) steel is a mature and reliable anti-corrosion material, and we widely use it in solar mounting structures because of its excellent overall performance. In this article, we focus on how you can select galvanized steel and its grades for solar mounting applications. We draw on publicly available data from CNKI (China National Knowledge Infrastructure) to explain the principles, advantages, application cases, and selection methods of HDG steel in solar mounting systems.
1. Introduction: The Wide Application of Hot Dipped Galvanizing in Solar Mounting
Photovoltaic power generation is a key part of the global "dual carbon" strategy, and it has developed rapidly in recent years. We now build PV power stations in a wide range of environments, from deserts and plains to rooftops and coastal areas. Solar mounting systems, which stay outdoors all year round, face various corrosive factors-including wind, rain, ultraviolet radiation, humidity, and salt spray (especially in coastal regions). According to relevant studies from CNKI, PV systems generally require a service life of no less than 25 years, and the corrosion resistance of mounting materials is the core factor that affects the system's long-term stable operation.
Hot dipped galvanizing is a classic metal anti-corrosion process, and we widely use it in solar mounting because of its mature craftsmanship, stable performance, and cost-effectiveness. Statistical data from CNKI shows that more than 70% of large-scale ground-mounted PV stations and 60% of distributed PV projects in China use HDG steel as the main material for their mounting structures. This widespread use is closely linked to HDG steel's excellent corrosion resistance: it effectively solves the problem of premature corrosion and damage of steel brackets in harsh outdoor environments, ensuring that PV modules operate safely and stably throughout their service life.
2. How Hot Dipped Galvanizing Works
The hot dipped galvanizing process for solar mounting steel is a metallurgical bonding process. We form a protective zinc layer on the steel surface by immersing pretreated steel into molten zinc. According to technical specifications in CNKI literature, the entire process consists of four key steps: surface pretreatment, molten zinc immersion, cooling, and post-treatment. Each step directly affects the quality of the zinc layer and the final product's anti-corrosion effect.
First, workers pretreat the surface of the solar mounting steel. This step includes degreasing, derusting, and fluxing, which removes oil stains, rust, and oxide layers from the steel surface-ensuring the zinc layer can bond firmly with the steel substrate. Next, they immerse the pretreated steel into a molten zinc bath, where we control the temperature between 460-480℃. At this high temperature, a series of metallurgical reactions occur between the iron on the steel surface and the zinc, forming a dense alloy layer (mainly Fe-Zn intermetallic compounds) between the steel substrate and the surface zinc layer. Finally, workers remove the steel from the zinc bath to cool it, and then perform passivation treatment to further enhance the zinc layer's corrosion resistance and appearance quality. The entire process results in a three-layer structure: "steel substrate – alloy layer – pure zinc layer," which provides comprehensive protection for the steel.
3. Key Advantages of HDG Steel for Solar Mounting
Combining relevant papers from CNKI and industry standards, HDG steel offers three core advantages in solar mounting applications-advantages that many other materials cannot match.
First, HDG steel has excellent corrosion resistance. The zinc layer formed by hot dipped galvanizing effectively isolates the steel substrate from external corrosive environments, such as oxygen, water vapor, and salt spray. Zinc also provides sacrificial anode protection: even if the zinc layer gets partially scratched, the zinc corrodes first, which protects the steel substrate from rust. CNKI test data shows that the average thickness of HDG layers for solar mounting steel is no less than 55μm, which complies with the national standard GB 50797-2012. Its corrosion rate in general outdoor environments is less than 0.01mm/year, so it can effectively resist corrosion for 20-25 years-fully meeting the service life requirements of PV systems. In high-salt coastal environments, you can increase the zinc layer thickness to over 100μm to further improve corrosion resistance, extending the service life to more than 30 years.
Second, HDG steel has strong zinc layer adhesion. The HDG zinc layer forms through a metallurgical reaction with the steel substrate, integrating with the steel and offering extremely strong adhesion. CNKI test data indicates that the adhesion of HDG layers can reach over 10MPa, which is much higher than the 3MPa adhesion requirement for solar mounting materials. Even under wind loads, vibration, and temperature changes during long-term use, it does not easily peel off or fall off-ensuring the structural stability of the mounting system.
Third, HDG steel has a long service life and low maintenance costs. It has excellent weather resistance and corrosion resistance, maintaining stable performance in harsh outdoor environments such as high temperatures, low temperatures, humidity, and salt spray. During the 25-year service life of a PV system, it basically requires no additional anti-corrosion maintenance, which greatly reduces the operation and maintenance costs of the PV station. Compared with other anti-corrosion methods (such as painting), HDG steel can save you more than 60% of maintenance costs over its entire service life, offering obvious economic advantages.
4. HDG Steel vs. Electro-Galvanized Steel for Solar Mounting
When you select galvanized steel for solar mounting, HDG steel and electro-galvanized steel are two common options. However, they differ significantly in terms of corrosion effect, cost, and applicable scenarios. Below, we provide a detailed comparison based on CNKI data and research results.
In terms of corrosion effect, the zinc layer of electro-galvanized steel is generally 5-30μm thick-much thinner than that of HDG steel (≥55μm). The electro-galvanized layer forms through physical deposition, so its adhesion to the steel substrate is weak, making it easy to peel off in harsh outdoor environments. CNKI test data shows that the outdoor service life of electro-galvanized steel is only 5-10 years, which fails to meet the 25-year service life requirement of PV systems. In contrast, HDG steel has a thick zinc layer and strong adhesion, with an outdoor service life 2-5 times that of electro-galvanized steel. Its advantages are particularly obvious in high-corrosion environments such as coastal areas.
In terms of cost, the unit price of electro-galvanized steel is 10%-15% lower than that of HDG steel. But from a whole-life cycle cost perspective, HDG steel is more cost-effective. Electro-galvanized steel requires re-anti-corrosion maintenance every 3-5 years, and the maintenance cost is high. CNKI cost analysis data shows that the total cost of electro-galvanized steel (including material and maintenance costs) over 25 years of service is 1.8-2.2 times that of HDG steel. Therefore, although HDG steel requires a higher initial investment, it saves you a great deal of maintenance costs in the long run.
In terms of applicable scenarios, electro-galvanized steel has poor corrosion resistance, so it is only suitable for low-corrosion environments, such as indoor distributed PV projects or areas with a dry climate and clean air. HDG steel, however, has strong adaptability, and you can use it widely in various PV installation scenarios-including desert and plain ground-mounted PV stations, rooftop distributed PV projects, and coastal high-salt PV projects. Especially in coastal areas, HDG steel is the preferred material for solar mounting because of its excellent resistance to salt spray corrosion.
5. How to Select Galvanized Steel and Its Grades for Solar Mounting
Selecting galvanized steel for solar mounting requires you to comprehensively consider the installation environment, service life requirements, structural bearing capacity, and cost factors. Based on CNKI research results and industry standards, here are the key points you should keep in mind.
First, determine the type of galvanized steel based on the corrosion environment. For general outdoor environments (such as inland plains and rooftops), you can select ordinary HDG steel, with a zinc layer thickness of no less than 55μm (complying with GB 50797-2012). For high-corrosion environments such as coastal and industrial areas, you should choose thickened HDG steel (zinc layer thickness ≥100μm) or hot-dip galvanized aluminum-magnesium steel-these materials have better corrosion resistance than traditional HDG steel. We do not recommend electro-galvanized steel for outdoor PV projects because of its poor corrosion resistance.
Second, select the appropriate galvanized steel grade based on bearing capacity requirements. According to the industry standard NB/T 10642-2021 recorded in CNKI, solar mounting steel should preferably use grades Q235, Q355, and S550, with quality meeting national standards such as GB/T 700 and GB/T 1591. For small and medium-sized distributed PV brackets with low bearing capacity requirements, Q235 grade HDG steel is a good choice, as it offers low cost and stable performance. For large-scale ground-mounted PV brackets and tracking brackets with high bearing capacity requirements, Q355 grade HDG steel is more suitable-it has higher strength and toughness, better meeting the requirements for structural stability. For PV projects with special requirements such as lightweight and high strength, you can select S550 grade high-strength HDG steel, but you should comprehensively consider the cost.
Third, pay attention to the quality of the galvanized layer. When you select HDG steel for solar mounting, you need to check whether the zinc layer thickness, adhesion, and uniformity meet national standards. According to test methods recorded in CNKI, you can use a thickness gauge to detect zinc layer thickness, and the scratch method to test adhesion. At the same time, choose products from regular manufacturers with complete quality inspection reports to ensure stable product quality.
6. Application Case: HDG Steel in Coastal PV Projects
Coastal areas, with high air humidity and high salt spray concentration, are typical high-corrosion environments-they place extremely high demands on the corrosion resistance of solar mounting materials. Let's take the Sanhang Dongying Offshore PV Project as an example. Located on the coast of Bohai Bay, this project faces severe salt spray corrosion and harsh environmental conditions. The project team chose thickened HDG steel as the main material for the solar mounting system and optimized the galvanizing process to ensure the corrosion resistance of the brackets.
According to project operation data recorded in CNKI, the HDG steel brackets used in the project adopt Q355B grade steel, with a zinc layer thickness of 100-120μm (complying with GB/T 13912-2020). After one year of operation, the bracket surfaces showed no signs of rust, peeling, or other issues, with a zinc layer retention rate of over 95%. The brackets maintained good structural stability, showing no deformation or damage under sea wind and salt spray. Compared with the original "galvanizing + painting" double anti-corrosion plan, using HDG steel not only reduced construction difficulty and cost, but also improved the durability of the mounting system. This case fully proves that HDG steel has excellent adaptability and corrosion resistance in harsh coastal high-salt environments, making it an ideal material for coastal solar mounting systems.
7. Conclusion
As the PV industry continues to expand and installation scenarios become increasingly diverse, the performance requirements for solar mounting materials are getting higher and higher. Hot dipped galvanized steel has become the preferred material for solar mounting systems, thanks to its excellent corrosion resistance, strong zinc layer adhesion, long service life, and high cost-effectiveness. When compared with electro-galvanized steel, HDG steel has obvious advantages in terms of corrosion effect and long-term use cost, making it more suitable for outdoor PV projects with high service life requirements.
When you select galvanized steel for solar mounting, you need to choose the type of galvanized steel (HDG steel is preferred for outdoor projects) based on the corrosion environment, select the appropriate grade (such as Q235, Q355, S550) based on bearing capacity requirements, and pay close attention to the quality of the galvanized layer. The coastal PV project case shows that HDG steel can effectively adapt to harsh environments such as high salt spray, ensuring the long-term stable operation of PV systems.
In conclusion, hot dipped galvanized steel fully meets the performance requirements of solar mounting systems in terms of corrosion resistance, structural stability, and cost-effectiveness, making it an ideal choice for solar mounting materials. With the continuous progress of galvanizing technology, HDG steel will be more widely used in the global PV industry, providing strong support for the sustainable development of the PV sector.
