Hot-Dip Zn-Al-Mg (ZAM) Coated Steel for Highway Guardrail
Hot-Dip Zn-Al-Mg (ZAM) Coated Steel for Highway Guardrails
MESCO supplies hot-dip zinc-aluminum-magnesium (Zn-Al-Mg, also known as ZAM) coated steel coils produced on a hot-rolled base, engineered specifically for road and bridge guardrail systems. The coating composition of Zn-6%Al-3%Mg delivers corrosion resistance up to six times that of conventional hot-dip galvanized (GI) steel, making it the preferred replacement for post-galvanized guardrails in coastal and high-humidity regions.
- Self-healing cut-edge protection
- High-strength grades up to 750 MPa
- 6000+ hours neutral salt spray resistance
- 1.5–6.0 mm × 900–1680 mm supply range
Why Zn-Al-Mg Outperforms Conventional Galvanized Steel
Superior Flat Corrosion Resistance
The Zn-6%Al-3%Mg coating outperforms pure zinc in ammonia, acid and alkaline environments.
Self-Healing Cut Edges
MgZn2 phases dissolve first and form a stable protective film that seals exposed cut edges.
High Surface Hardness
140–160 HV versus 55–65 HV for galvanized steel, reducing scratch and wear during forming.
High-Strength Grades
Up to 750 MPa enables thinner, lighter guardrail designs without compromising impact safety.
Excellent Formability
180° bend without substrate cracking, plus low dynamic friction for easier stamping.
Reliable Weldability
Stable resistance spot-welding windows and low-spatter arc welding with 80% Ar + 20% CO2.
Traditional Galvanized vs Zn-Al-Mg Guardrail Steel
Hot-Dip Galvanized (GI)
- Zinc layer 55–80 μm, service life only 10–15 years
- Insufficient resistance for coastal and high-humidity areas
- Increasing coating to 140 μm+ raises cost and forming difficulty
- Cut edges corrode easily after fabrication
Zn-Al-Mg (ZAM)
- Self-healing cut edges, 3–6× longer service life
- 750 MPa high-strength steel enables lightweight barriers
- Better safety for typhoon-prone coastal expressways
- Lower zinc consumption, eco-friendly and cost-effective
Technical Specifications
| Property | Specification |
|---|---|
| Coating composition | Zn-6%Al-3%Mg (ZAM) |
| Coating weight | 80–450 g/m2 (double-sided); guardrail typical 275 g/m2 or 310–350 g/m2 |
| Thickness range | 1.5–6.0 mm |
| Width range | 900–1680 mm |
| Strength grades | 280–750 MPa |
| Surface treatment | Passivation, anti-fingerprint, oiling |
| Corrosion test | Neutral salt spray — GB/T 10125 |
Available Grades & Mechanical Properties
| Grade | Yield strength (MPa ≥) | Tensile strength (MPa ≥) | Elongation (%) |
|---|---|---|---|
| S280GD+ZMA | 280 | 360 | 18 |
| S350GD+ZMA | 350 | 420 | 16 |
| S420GD+ZMA | 420 | 480 | 15 |
| S450GD+ZMA | 450 | 510 | 14 |
| SGH340D+ZMA | 245 | 340 | 20 |
| SGH440D+ZMA | 335 | 440 | 18 |
| H700HLD+ZMA | 600 | 700 | 12 |
| H750HLD+ZMA | 700 | 750 | 20 |
Applications
Purpose-built for highway and bridge guardrail systems, and equally reliable for photovoltaic, construction and warehousing projects.
Corrugated Beam Guardrail
3.5–6.0 mm, SGH340D+ZMA
Guardrail Posts & Columns
Square-tube and clamp fabrication
Movable Safety Barriers
H750HLD+ZMA, 1.8–3.0 mm
PV Mounting Structures
Solar and photothermal frames
Construction Framing
Light steel structure
Warehouse Racking
Long-life rack systems
Frequently Asked Questions
How does Zn-Al-Mg coated steel differ from hot-dip galvanized (GI) steel?
The Zn-6%Al-3%Mg coating forms a dense, self-healing layer that seals cut edges and resists corrosion roughly 3–6× longer than pure zinc at the same coating weight. It also offers higher surface hardness and better ammonia and acid/alkali resistance.
What sizes, coating weights and grades can MESCO supply?
We supply thickness 1.5–6.0 mm × width 900–1680 mm, coating weights 80–450 g/m2 (double-sided), and strength grades from 280 to 750 MPa.
What is the MOQ and lead time?
Typical MOQ is one 20 ft container (about 25 metric tons), with a production lead time of approximately 20–30 days. Free samples and mill test certificates are available on request.
Need a Zn-Al-Mg Coated Steel Quote?
Tell us your grade, thickness, coating weight and quantity — our team will respond with pricing, lead time and free sample availability within 24 hours.
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