The GI (Hot-Dip Galvanizing) and ZAM (Zinc-Aluminum-Magnesium Alloy Coating) standards commonly used for highway guardrails mainly cover material performance, galvanized layer thickness, corrosion resistance grade, and test methods, with clear specifications both domestically and internationally, as shown in the table below:
| Standard System | Applicable Region | Core Requirements | Common Zinc Layer/Coating Thickness | Application Features |
| AASHTO M180 | USA & Parts of Americas | Specifies material, dimensions, galvanized layer thickness, and mechanical properties of corrugated steel plates for guardrails | Type I ≥550 g/m²; Type II ≥1100 g/m² | Mainstream in North America, with corrosion resistance graded; paired with ASTM A653 hot-dip galvanizing inspection |
| EN 1317 | Europe | Covers guardrail safety performance and anti-corrosion requirements | Minimum hot-dip galvanizing thickness: 80 μm (approx. 550 g/m²); higher requirements may apply in some countries | Detailed safety grade classification, linked to anti-corrosion requirements; widely used |
| JTG/T D81-2017 + GB/T 31439.1/2 | China | Specifies guardrail structure, anti-collision grade, and anti-corrosion treatment | Average hot-dip galvanizing thickness: 85 μm (approx. 580 g/m²); some projects may require thickness above 1100 g/m² | Balances anti-corrosion and anti-collision performance; SB/SA grades commonly used for highways |
| AS/NZS 3845 | Australia/New Zealand | Specifies materials and galvanized layers for corrugated steel guardrails | 550 g/m² or 1100 g/m² commonly used | Suitable for coastal high-salt-spray environments |
| ZAM (Enterprise Standard) | Global | Zinc-aluminum-magnesium alloy coating (no unified international standard) | 100–300 g/m² to achieve excellent corrosion resistance | High corrosion resistance and self-repair ability; used to replace GI in harsh environments |
GI Standards: Focus on zinc layer thickness and uniformity, achieving anti-corrosion through hot-dip galvanizing process. Common thicknesses include 550 g/m², 850 g/m², and 1100 g/m²; higher thickness means stronger corrosion resistance.
ZAM Standards: Zinc-aluminum-magnesium alloy coating offers stronger resistance to salt spray and scratches. Under the same thickness, its corrosion resistance is better than GI. Some enterprises claim that 100–300 g/m² of ZAM can replace 550–1100 g/m² of GI.
Coastal and heavily polluted areas: Priority should be given to ZAM 200–250 g/m². Although the initial investment is slightly higher, the total life-cycle cost is lower.
General inland areas: GI 850–1100 g/m² is a reliable option. If low maintenance is a priority, you can upgrade to ZAM 150–200 g/m².
Reconstruction and expansion projects: ZAM has more advantages in shortening the construction period, reducing galvanizing processes, and minimizing on-site welding damage.
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