Photovoltaic (PV) mounting structures are typically located in harsh environments such as coastal mudflats, deserts, gobi, and water surfaces. According to the ‘NB/T 10115—2018 Technical Code for PV Mounting Structure Design’, the service life of PV supports should not be less than 25 years, which places high demands on corrosion resistance.
The structure mainly consists of foundations, uprights, beams, purlins, diagonal supports, and fittings. Except for foundations that use hot-dip galvanized Q235 and Q335 materials with thicknesses of 4–12 mm, most other components use 1.5–8.0 mm thick HDG Q235/Q335. High-strength steels like S350GD and S420GD are increasingly used, typically in 1.5–5.0 mm thicknesses. Most domestic PV projects use hot-rolled strip steel, cold-formed and then hot-dip galvanized (≥60 μm zinc layer). This method is costly and environmentally demanding due to cleaning, pickling, and logistics, often exceeding the capabilities of small-scale galvanizing plants.
2. Development and Application of Thermal-Based Zn-Al-Mg Materials
Zn-Al-Mg coated steel is derived from traditional hot-dip zinc by adding Al, Mg, and trace alloys. Products are categorized by aluminum content: low, medium, and high. Brands like ZM EcoProtect® (Thyssenkrupp) and Corrender® (Voestalpine) use low-aluminum compositions.
Advantages include:
① Superior cut-edge corrosion resistance
② 3–7x better neutral salt spray resistance; 2x better atmospheric durability
③ 15% lower friction coefficient
④ 3x higher surface hardness than pure zinc coatings
Global development began in Japan (e.g., SuperZinc, ZAM, Super Dyma), then Europe and Australia (Next Generation ZINCALUME). Chinese manufacturers now offer various Zn-Al-Mg coatings tailored for automotive, home appliance, and construction use. Thermal-based types use pickled hot-rolled coil as substrate, allowing for thicker specifications and streamlined, eco-friendly processing.
3. Advantages of Thermal-Based Zn-Al-Mg in PV Applications
① Cost reduction: Continuous coating over hot-rolled base eliminates post-galvanizing. Material costs drop by ~¥800/t, plus logistics savings.
② Environmental benefit: Avoids cold-rolling; Shougang is a rare A+ rated green steel plant in Hebei, outperforming small galvanizers.
③ Self-healing: Oxidized layer protects cut or scratched surfaces. Salt spray tests show no red rust after 4000 hours on cuts and surfaces.
④ Material stability: Strength retention avoids weakening from post-forming galvanizing. Consistent specs suit standardization and mass production.
Test results of thermal-based Zn-Al-Mg materials with different thicknesses after 4000 hours of neutral salt spray exposure: left – 1.5 mm, right – 3.0 mm.
Test results at the punched areas of thermal-based Zn-Al-Mg materials with different thicknesses after 4000 hours of neutral salt spray exposure: left – 1.5 mm, right – 3.0 mm.
4. Shougang product features
SHOUGANG SOZAMC® Zn-Al (6%)-Mg (3%) Alloy Hot-Rolled Steel Sheets
In terms of corrosion resistance，SHOUGANG SOZAMC® Zn-Al-Mg alloy hot-rolled steel sheets is 3 times better than hot-dip zinc-coated steel sheets with the same coating weight, and the excellent corrosion resistance is achieved on cut edge. It can be used as a substitute for post hot-dip galvanizing in some ways.
5. Corrosion resistance of flat sections
In neutral salt spray test,SOZAMC® is a corrosion resistant products that is 6 times stronger resistance than that of a normal hot-dip galvanized steel sheet.
Corrosion resistance of cut edge
The exposed cut edge of substrate is oxidized due to rain,condensation,etc.Excellent corrosion resistance is achieved on cut edge parts by covering the ends with a fine zinc-based protective film that contains Al and Mg leaching from the coating layer.
5.1 Planar corrosion resistance (SST)
In neutral salt spray test, SOZAMC® is a corrosion resistant product that is 6 times stronger resistance than that of a normal hot-dip galvanized steel sheet.
Z1200, 800 hours ZMA275, 5040 hours
5.2 Corrosion resistance on cut section (SST)
In neutral salt spray test, the corrosion resistant of SOZAMC® on cut section is 20 times stronger resistance than that of a normal hot-dip galvanized steel sheet.
5.3 Corrosion resistance on punch cut section(SST)
SOZAMC®shows excellent corrosion resistance on punch cut section of diff erent thickness steel plate.
5.4 Corrosion resistance on bending part(SST)
SOZAMC®shows excellent corrosion resistance on the bending parts.90 ° bending aff ects little on the corrosion resistance。SOZAMC® gets no red rust after 5000h SST.
6. Conclusion
Shougang’s thermal-based Zn-Al-Mg products offer excellent surface quality, stability, eco-friendliness, and cost-effectiveness. These materials have been increasingly adopted in the PV industry, recognized by major power companies, and bring strong economic returns for manufacturers and project owners. They are highly recommended for widespread adoption.
* SOZAMC® is a registered trademark of Shougang for ZnAlMg(Medium Al) coated steel sheet. The coating contains high aluminum（5~7%） and magnesium（2~4%）. The corrosion resistance of the coating is more than 3 times that of the zinc coating. The cutting edge also has good corrosion resistance. It can greatly reduce the amount of hot-dip zinc, thus has good substitutability for hot dip galvanizing process. It can be widely used to manufacture outdoor steel structures.