ZAM zinc-aluminum-magnesium VS GI Galvanized Steel
1.What is Zinc-Aluminum-Magnesium (ZAM)?
Zinc-aluminum-magnesium (ZAM) is a high-performance metallic coating applied to steel designed to offer superior corrosion resistance, durability, and heat resistance compared to traditional galvanizing (zinc-only coatings). The coating combines zinc (Zn), aluminum (Al), and magnesium (Mg), which provides unique advantages in various applications.
2.What is Hot-dip galvanizing? (HDG)?
Hot-dip galvanization is a form of galvanization. It is the process of coating iron and steel with zinc, which alloys with the base metal surface when immersing the metal in a bath of molten zinc at a temperature of around 450 °C (842 °F). When exposed to the atmosphere, the pure zinc (Zn) reacts with oxygen (O2) to form zinc oxide (ZnO), which further reacts with carbon dioxide (CO2) to form zinc carbonate (ZnCO3), a usually dull grey, fairly strong material that protects the steel underneath from further corrosion in many circumstances.
ZAM GI Steel General Specification
GNEE STEEL produces coated steel materials in accordance with international standards such as ASTM, JIS, GB, EN, ISO, etc., including zinc-plated steel, zinc-aluminum-zinc-plated steel, zinc-aluminum-magnesium-zinc coating steel, and so on.
| Parameter | Typical Specifications for ZAM | Typical Specifications for GI |
| Coating Weight | ZAM60/120/180 (g/m²) | Z60/120/180/275 (g/m²) |
| Substrate Strength | DX51D~S550GD+ZAM | DC01/DX51D~S550GD+Z |
| Surface Treatment | Chromium-free Passivation + Fingerprint Resistance (Standard) | Chromic Acid Passivation (Requires additional environmental treatment) |
| Tolerance Accuracy | Thickness ±0.03mm (<1mm sheet) | ±0.05mm |
ZAM GI Steel Composition
GI steel is a pure zinc coated steel, ZAM steel is a Zn-Al-Mg ternary coated steel, as ZAM is a surface protection upgrade program.
| Parameter | Zinc-Aluminum-Magnesium Steel (ZAM) | Galvanized Steel (GI) |
| Coating Composition | Zn-6~11%Al-1~3%Mg-Si | Zn≥99% |
| Coating Structure | MgZn₂/MgZn₁₁ Eutectic + Al-rich Dendrites | Pure Zn layer (η phase) |
| Coating Density | 3.75 g/cm³ (thinner, more material-efficient) | 7.14 g/cm³ |
| Protection | 1. Al₂O₃ Barrier
2. Zn/Mg Sacrificial Anode 3. MgO Self-healing |
Single Sacrificial Anode (Zn) |
ZAM GI Steel Mechanical Properties Differences
The mechanical properties of coated steels are affected by a number of factors relating to the substrate grade and the coating, with ZAM having superior ductility and double the fatigue life for the same strength grade.
| Performance | ZAM350 | GI S350GD | Advantage |
| Yield Strength (MPa) | 350 ± 30 | 350 | → |
| Tensile Strength (MPa) | 420 ± 40 | 420 | → |
| Elongation (%) | 22 (A80mm) | 18 (A80mm) | +22% |
| Fatigue Limit (MPa) | 260 | 190 | +37% |
| Hardness (HV) | 180 | 150 | +20% |
ZAM GI Steel Physical Properties
The physical properties of ZAM Zinc-Aluminum-Magnesium and GI galvanized steel are mainly influenced by the chemical composition, the coating process, the heat treatment process, and other aspects.
| Property | ZAM | GI | Impact |
| Thermal Conductivity (W/m·K) | 60 | 50 | Faster heat dissipation by 10% |
| Resistivity (μΩ·cm) | 15 | 6 | Requires higher welding current |
| Coefficient of Thermal Expansion (×10⁻⁶/K) | 13.5 | 12.0 | Differences in high-temperature deformation |
| Reflectivity (%) | 75~80 | 40~50 | 30% energy-saving in cooling |
ZAM GI Steel International Standard System
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Core International Standard for Galvanized Steel (GI)
| Standard | Key Parameter Requirements |
| ASTM A653/A653M (US) | – Coating designation: G60/G90/G115 (oz/ft²)
– Salt spray requirement: G90 ≥ 720h, red rust ≤ 5% |
| EN 10346:2015 (EU) | – Coating designation: Z100/Z180/Z275 (g/m²)
– Mechanical properties: S250GD-S550GD (strength grade) |
| JIS G 3302 (Japan) | – Coating designation: Z12/Z18/Z22 (g/m²)
– Surface treatment: C (chromic acid passivation)/N (untreated) |
| GB/T 2518-2019 (China) | – Coating designation: Z60/Z80/Z180 (g/m²)
– Surface structure: N (normal zinc flower)/M (small zinc spangle) |
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Core International Standard for Zinc-Aluminum-Magnesium (ZAM) Steel Sheets
| Standard Number | Key Parameters |
| EN 10346:2020 (EU) | – ZMA180: Al 6-11% + Mg 1-3%
– Salt spray requirement: ≥1500h (red rust ≤ 5%) |
| ASTM A1079 (US) | – Coating designation: ZM50/ZM100 (g/m²)
– Composition: Al 1-22% + Mg 0.01-10% |
| JIS G 3323:2022 (Japan) | – DX1 (low aluminum): Al 1-3.5% + Mg 0.1-1%
– DX2 (medium aluminum): Al 3.5-9% + Mg 1-3% – DX3 (high aluminum): Al 9-13% + Mg 1-4% |
| GB/T 14978-2023 (China) | – ZAM150: Al 4-15% + Mg 1-3%
– Edge protection: ≥1mm (after 480h salt spray) |
Applicable Scenario Differences
- ZAM Zinc Aluminum Magnesium Applicable Scenarios
Extreme corrosive environments: seaside buildings, port facilities, shipbuilding, chemical plants, refineries, etc.
High-demand processing scenarios: manufacture of automobile bodies, chassis and other components, transmission towers, substations, etc.
Scenarios that require long term stability: highway guardrails, outdoor billboards
Scenarios with high environmental protection requirements: solar panel brackets, wind power towers, green buildings
- Galvanized Steel GI Applicable Scenarios
General anticorrosive demand scenarios: steel structure factory buildings, warehouses, park benches, garbage cans, etc.
Cost-sensitive scenes: shells of refrigerators, washing machines, etc., greenhouse greenhouses, livestock and poultry houses, etc.
Short-term or temporary scenarios: temporary booths, movable scaffolding, construction hoardings at building construction sites
Scenarios that do not require high material performance: drainage pipes, ventilation pipes, machinery manufacturing, etc.
ZAM Zinc Aluminum Magnesium can maintain structural integrity and aesthetic appearance and excellent corrosion resistance in long-term exposure to outdoor environments. Therefore, ZAM Zinc Aluminum Magnesium may be preferred for long-term projects in extreme or harsh corrosive environments where high demands are made on material durability, processability, or environmental friendliness.
Galvanized steel provides basic corrosion protection at a lower cost, so ZAM steel GI is preferred in applications where corrosion environments are relatively benign, where material costs are sensitive, where there is a need to control the initial investment, or where material performance is not critical.
FAQ
1. Is Zn-Al-Mg steel more expensive than Galvanized steel?
The initial per-ton price is usually higher than standard GI. However, because it lasts much longer and often allows for a lower coating weight to achieve the same protection, the Life Cycle Cost (LCC) is typically lower.
2. How does it save time in manufacturing?
Since the material can be cut and formed without losing its edge protection (due to the self-healing property), manufacturers can skip the secondary "batch-galvanizing" step after fabrication.
3. Does Zn-Al-Mg steel support sustainability goals?
Yes. Its extended lifespan reduces the frequency of replacement, and the manufacturing process often uses less zinc than heavy-duty galvanizing, resulting in a lower environmental footprint.
4. Does it require special paint or powder coating?
No. It provides an excellent substrate for painting. The stable oxide layer ensures high paint adhesion, similar to or better than galvanized steel.
5. What international standards apply to Zn-Al-Mg steel?
It is typically produced according to standards such as EN 10346 (for continuously hot-dip coated steel products) or equivalent national and regional industrial standards.
