I. Grades
What to look for regarding grades.
Based on practical application, grades are assessed as follows: ISO 9223 (understanding atmospheric corrosion and the corrosive environment affecting PV mounts; to design specific galvanizing thicknesses for different atmospheric environments, one must understand the ISO 9223 standard; ISO 9223 categorizes atmospheric corrosion into six levels ranging from C1 to CX; first-year corrosion rate); C1–C5 (common corrosion grade classifications); C1 (Very Low: heated buildings, clean atmospheres, offices, schools, hotels); C2 (Low: unheated buildings, rural atmospheres, steel mass loss 1.3–25 µm/year); C3 (Medium: urban/industrial, moderate SO2, city centers, light industrial plants, coastal low-salt areas, 25–50 µm/year); C4 (High: industrial/coastal, moderate salt, chemical plants, coastal areas, swimming pools, 50–80 µm/year)—a comprehensive look at the grades: ISO 9223, C1–C5, C1, C2, C3, and C4.
II.
Standards
What to look for regarding standards.
Regarding standard practices, the standards are interpreted as follows: GB 50797 (China Academy of Building Research) — For PV mounting structures, anti-corrosion design must be tailored to local conditions, considering factors such as the operating environment, service life, and construction/maintenance requirements; atmospheric corrosion environment classifications must follow the values in Appendix D of this standard. Hot-dip galvanizing (China Academy of Building Research) — Anti-corrosion measures for ordinary carbon steel structures should ideally combine methods such as hot-dip galvanizing, zinc-aluminum bimetallic coatings, and zinc-aluminum-magnesium alloy coatings; the minimum average thickness of the anti-corrosion layer must meet corrosion allowance requirements for the specific atmospheric environment over the service life; the average thickness of the hot-dip galvanized layer must not be less than 55 μm. ISO 1461 (PVrack) — Specifies galvanization methods for solar mounting structures; ISO 1461:2022 (Hot-dip galvanized coatings on fabricated iron and steel articles) is the global standard for post-fabrication batch hot-dip galvanizing (HDG), specifying minimum coating thickness by section category and test methods (magnetic measurement per ISO 2178), as well as repair requirements (maximum 0.5% uncoated area, minimum 100 μm repair thickness). GB/T 13912 (National Group Standard Information Platform) — For distributed PV system mounting structures (T/CASME), when hot-dip galvanizing is used for anti-corrosion, both the average and local zinc coating thicknesses must comply with GB/T 13912 specifications; requirements also apply to average coating thickness when fluorocarbon or polyurethane spray coatings are used. T/CPIA 0013 (qixin) — For PV mounting structures (T/CPIA 0013—2019), the salt spray corrosion resistance of steel structures is tested in accordance with GB/T…
…conduct the Neutral Salt Spray (NSS) test in accordance with the provisions of 10125 for the duration specified in Table 7, and evaluate the results per GB/T 6461; test the thickness, appearance, and adhesion of the hot-dip galvanized coating on the steel support structure in accordance with GB/T 13912; NB/T 10642—General Institute of Hydropower and Water Resources Planning and Design (regarding the *Technical Specification for Anti-corrosion of Offshore Photovoltaic Structures*): domestically, only NB/T 10642-2021 (*Technical Requirements for Photovoltaic Power Station Support Structures*) specifies anti-corrosion measures for support components; however, that standard primarily targets onshore photovoltaic products—with atmospheric corrosion categories reaching only up to C4—and does not address the C5/CX categories commonly encountered in offshore environments (such as seawater and marine sediment zones); General Institute of Hydropower and Water Resources Planning and Design)—Standards to review: GB 50797, ISO 1461, GB/T 13912, T/CPIA 0013, and NB/T 10642;
these six standards must be properly addressed.
III. Thickness
What to look for regarding thickness.
Regarding thickness specifications: 55 μm — *Code for Design of Photovoltaic Power Stations* (GB 50797-2012, Section 6.8.10: Anti-corrosion treatment for steel mounting structures should preferably utilize hot-dip galvanizing, with an average coating thickness of no less than 55 μm; aluminum alloy structures require surface anti-corrosion treatment, such as anodizing); C1–C3 — China Academy of Building Research (for structural components made of continuously hot-dip galvanized or zinc-alloy coated steel sheets/strips in regions with C1–C3 corrosivity categories, the coating mass should be no less than 180 g/m² [total for both sides] for galvanized steel or 100 g/m² [total for both sides] for Al-Zn coated steel); C4, C5 — China Academy of Building Research (for regions with C4 and C5 corrosivity categories, the coating mass should be no less than 275 g/m² [total for both sides] for galvanized steel or 150 g/m² [total for both sides] for Al-Zn coated steel); 65 μm — Douyin (regarding the selection of PV mounting structures: hot-dip galvanizing offers numerous advantages; it is the most mature and longest-established process).
…and the technology is highly stable, offering a long anti-corrosion lifespan. National standards require an average coating thickness of no less than 65 microns, ensuring no rust for 25 years in normal environments; 85 microns—(Douyin: PV mounting pitfalls, Part 3—choosing the wrong zinc layer leads to premature plant failure; the zinc layer is a core indicator of a PV mount’s anti-corrosion lifespan, and the “micron” rating cited in the industry refers to the average of three test points; standard hot-dip galvanized stock typically has a thickness of 20–30 microns, providing a 10–15 year lifespan; high-zinc PV mounts feature a 65-micron layer, guaranteeing 25 years in general environments; highly corrosive environments—such as coastal areas, chemical plants, and sewage treatment facilities—generally require 85 microns or more); non-linearity—(Douyin: Is thicker always better for PV mount zinc layers? The corrosion resistance of hot-dip galvanized zinc layers does not increase linearly; beyond a certain point, additional thickness yields diminishing returns in protective effectiveness; greater thickness also drives up processing costs)—Six thickness benchmarks: 55μm, C1–C3, C4, C5, 65 microns, and 85 microns;
ensure the thickness meets these six standards.
IV. Environment
What to consider regarding the environment.
Based on environmental practices, the classification is as follows: C4—PVrack (Corrosion Standards for Solar Mounting Systems; coastal solar farms near saltwater with moderate salt spray are generally classified as C4 “High”; if the project is located directly on the beachfront or offshore, exposed to constant heavy salt mist and high humidity, it escalates to the most severe category, C5 “Very High”); C3—Solaracks (Hot-humid and corrosive engineering solar mounting for tropical APAC markets; for C3 sites, the baseline is hot-dip galvanizing (HDG) per ISO 1461 with a zinc coating thickness of ≥85 μm on sections thicker than 6 mm; this provides approximately 15–20 years of corrosion protection in a true C3 environment); ZAM—Solaracks (For C4 sites, HDG alone is marginal; ZAM Zn-Al-Mg alloy steel is strongly recommended due to ZAM’s self-sealing corrosion product properties); 70µm—Anern Store (Procurement specifications for galvanized racking: C2—Temperate, low-pollution rural, 70 µm, 30–60 years; C3—Urban/industrial, moderate SO2 pollution, 85 µm, 20–40 years; C4—Industrial areas/coastal, moderate salinity, 100 µm, 10–20 years); Salt Spray—qixin (PV mounting systems T/CPIA 0013—2019, Table 6: Salt spray corrosion resistance for steel mounts—corrosion grade “Low Corrosion,” neutral salt spray test duration 96h, protection rating Rp≥9; salt spray corrosion resistance for aluminum alloy mounts per GB/T…)
…conduct the Copper-Accelerated Acetic Acid-Salt Spray (CASS) test in accordance with the 12967.3 standard; for coastal areas—remember one principle: select materials based on the corrosive environment. Category 1 (high corrosion risk: seaside, near-shore, high-altitude areas, chemical parks, heavy industrial zones): use hot-dip galvanizing directly, ensuring a coating thickness of over 85 microns. Category 2 (moderate risk: inland cities, general industrial areas with humid air but no strong corrosivity): hot-dip galvanizing with a thickness of over 65 microns is the safest choice. Consider these six environmental factors: C4, C3, ZAM, 70µm, salt spray, and coastal location—ensure all six are properly evaluated.
V.
Selection
What to consider when selecting the product.
Based on selection practices, here is how to evaluate the 85μm specification: 85μm — Corrosion and Protection (Common anti-corrosion techniques for PV steel mounting structures in coastal environments; hot-dip galvanizing involves using molten zinc to form a metallurgically bonded zinc-iron alloy layer on the steel surface; requirements generally dictate a uniform surface free of zinc nodules that could impede installation; for structural components in coastal areas, the hot-dip galvanized layer thickness generally must not be less than 85μm; traditional hot-dip galvanized coatings face issues such as poor microstructural uniformity and suboptimal corrosion resistance); 85µm — Solaracks (HDG, ZAM, or Stainless; solar installations typically fall into corrosivity categories C2 through C5 depending on location and proximity to the coast or industrial sources; C2: Rural inland dry climate, HDG to ISO 1461 (85µm min), standard specification for 50+ year service life; Solaracks); Zinc-Aluminum-Magnesium — Douyin (Choosing the wrong material for PV mounts can lead to rust-through before the power plant recoups its investment; comparison of three mainstream mounting materials: Hot-dip galvanized steel—coating thickness ≥80μm, high cost-performance, common in early projects, but prone to coastal corrosion with a 15–20 year lifespan; Zinc-Aluminum-Magnesium steel—superior corrosion resistance, the preferred mainstream choice, optimal cost-performance, self-healing coating, 25+ year lifespan; Aluminum alloy 6063-T5 profiles; Douyin); C5/CX — Tianjin Zhongtong Dingxing (Lifecycle Optimization Solution; Thickness Classification: C4 Environment/Inland—minimum thickness ≥85μm [600g/m²], average thickness ≥95μm; C5/CX Environment/Coastal or Industrial Area—minimum thickness ≥100μm [700g/m²], average thickness ≥110μm; Process Identification: Hot-dip galvanized surface)
