Hot-Dip Zn-Al-Mg (ZAM) Coated Steel for Highway Guardrails
MESCO Group 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 Zn-6%Al-3%Mg delivers corrosion resistance up to six times that of conventional hot-dip galvanized steel, making it the preferred replacement for post-galvanized guardrails in coastal and high-humidity regions. The material is available in 280 to 750 MPa strength grades with coating weights from 80 to 450 g/m² (double-sided).
Key Features
Six engineering advantages set Zn-Al-Mg coated steel apart from traditional galvanized guardrail material.
Self-Healing Cut-Edge Protection
Magnesium-rich MgZn² phases dissolve first and form a stable Zn&sup5;(OH)&sup8;Cl²·H²O film that seals exposed cut edges and stops corrosion from spreading.
Up to 6× Corrosion Resistance
Neutral salt spray testing (GB/T 10125) exceeds 6,000 hours at a 275 g/m² double-sided coating, versus roughly 1,200 hours for pure zinc.
High Surface Hardness
140 to 160 HV, far harder than galvanized steel at 55 to 65 HV, giving superior scratch and wear resistance during forming and handling.
High Strength up to 750 MPa
Enables thinner, lighter guardrail designs that reduce weight without compromising impact-safety performance.
Excellent Formability & Weldability
180° bend without substrate cracking, plus stable resistance spot-welding and arc-welding process windows for fabrication.
Lower Cost & Eco-Friendly
Thinner, lighter coatings achieve equal or better protection, reducing zinc consumption and total cost of ownership.
Technical Specifications
| Property | Specification |
|---|
| Coating composition | Zn-6%Al-3%Mg (ZAM) |
| Coating weight | 80 to 450 g/m² (double-sided); guardrail typical 275 or 310 to 350 g/m² |
| Thickness range | 1.5 to 6.0 mm |
| Width range | 900 to 1,680 mm |
| Strength grades | 280 to 750 MPa |
| Surface treatment | Passivation, anti-fingerprint, oiling |
| Corrosion test | Neutral salt spray, GB/T 10125 |
Available Grades
| Grade | Yield strength (MPa) | Tensile strength (MPa) | Elongation (%) |
|---|
| S280GD+ZMA | 280 | 360 | 18 |
| S320GD+ZMA | 320 | 390 | 17 |
| S350GD+ZMA | 350 | 420 | 16 |
| S390GD+ZMA | 390 | 460 | 16 |
| S420GD+ZMA | 420 | 480 | 15 |
| S450GD+ZMA | 450 | 510 | 14 |
| SGH340D+ZMA | 245 | 340 | 20 |
| SGH400D+ZMA | 295 | 400 | 18 |
| SGH440D+ZMA | 335 | 440 | 18 |
| SGH490D+ZMA | 365 | 490 | 16 |
| 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 applications.
Corrugated Beam Guardrail
Guardrail Posts & Columns
Movable Safety Barriers
PV Mounting Structures
Construction Framing
Warehouse Racking
Livestock Buildings
Highway Signage
Traditional Galvanized vs Zn-Al-Mg Guardrail Steel
Hot-Dip Galvanized (GI)
- Zinc layer 55 to 80 µm, service life only 10 to 15 years
- Insufficient corrosion resistance for coastal and high-humidity areas
- Thicker coatings raise cost and forming difficulty
- Cut edges corrode easily after fabrication
Zn-Al-Mg (ZAM)
- Self-healing cut-edge protection, 3 to 6× longer service life
- High-strength steel enables lightweight, thinner barrier designs
- Better safety performance for typhoon-prone coastal expressways
- Lower zinc consumption, eco-friendly and cost-effective
Frequently Asked Questions
How does Zn-Al-Mg coated steel differ from hot-dip galvanized steel?
The Zn-6%Al-3%Mg coating forms a dense, self-healing protective layer that seals cut edges and resists corrosion roughly 3 to 6 times longer than pure zinc at the same coating weight. It also offers higher surface hardness and better ammonia, acid and alkali resistance.
What sizes, coating weights and grades can MESCO supply?
Thickness 1.5 to 6.0 mm by width 900 to 1,680 mm, coating weights 80 to 450 g/m² (double-sided), and strength grades from 280 to 750 MPa, covering heavy-gauge standard guardrail steel and high-strength movable barrier steel.
What is the MOQ and lead time?
Typical MOQ is one 20 ft container, about 25 metric tons. Production lead time is approximately 20 to 30 days after order confirmation. 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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