ZAM (Zinc-Aluminum-Magnesium) coated steel is an upgraded alternative to conventional hot-dip galvanized steel and aluminum-zinc coated steel. It is widely used for ZAM steel tubes, ZAM steel coils, and ZAM steel sheets. Featuring superior corrosion resistance, excellent scratch resistance and extended service life, ZAM coating solves the pain points of short anti-rust cycles and high maintenance frequency for ordinary coated steel.
This document compiles the latest internationally accepted ZAM coating standard specifications, conversion parameters, and scenario-based selection schemes to help you avoid procurement quality risks.
What is ZAM Coating?
ZAM is a ternary alloy coating of Zinc (Zn) – Aluminum (Al) – Magnesium (Mg), with typical composition as below:
| Element | Content |
|---|---|
| Zinc (Zn) | Balance |
| Aluminum (Al) | Approx. 6% |
| Magnesium (Mg) | Approx. 3% |
Under identical service conditions, the anti-rust service life of ZAM steel is generally 3–5 times that of conventional hot-dip galvanized steel. It is suitable for high-corrosion environments, with core applications including:
- Coastal high salt-spray areas
- Industrially polluted zones
- Environments exposed to road de-icing salts
- Long-lifespan infrastructure projects
Performance Comparison: ZAM Coating vs Hot-Dip Galvanized Coating
| Performance | Hot-Dip Galvanized (HDG) | ZAM Coating |
|---|---|---|
| Corrosion Resistance | Reference benchmark | Service life extended by 3–5 times |
| Cut Edge Protection | Fair | Excellent (Mg enhances protection on cut edges) |
| Alkali Resistance | Fair | Better |
| Salt Spray Performance | Standard | Markedly improved |
| Weldability | Good | Good |
| Surface Appearance | Standard grey | Smooth and uniform |
Magnesium is the critical element. It stabilizes corrosion products and forms a dense protective layer at cut edges and scratched areas. This explains why ZAM coating delivers outstanding performance on cut sections of steel tubes, coils, and sheets.
ZAM Coating Thickness & Weight Comparison
Conversion Notes
The density of ZAM alloy is approximately 6.6 g/cm³. Conversion formulas are as follows:
- Single-side coating weight (g/m²) = Single-side thickness (µm) × 6.6
- Total double-side coating weight (g/m²) = Single-side coating weight × 2
- Single-side thickness (µm) = Total double-side coating weight ÷ 2 ÷ 6.6
Note: Coating weight is normally stated as total weight on both sides (g/m²). Some standards calculate on a single-side basis. Always confirm with your supplier whether the quoted value is single-sided or double-sided during procurement.
ZAM Coating Grades, Thickness & Weight Table
| Coating Grade | Total Double-Side Coating Weight (g/m²) | Minimum Single-Point Coating Weight (g/m²) | Typical Single-Side Thickness (µm) | Core Application Scenarios |
|---|---|---|---|---|
| ZM30 | 30 | 25 | 2–3 | Indoor fittings, light-duty dry environments |
| ZM40 | 40 | 35 | 3–4 | Indoor structural tubes and sheets |
| ZM50 | 50 | 45 | 3–4 | Indoor fittings, light-duty dry environments |
| ZM60 | 60 | 50 | 4–5 | General indoor, mild outdoor exposure |
| ZM70 | 70 | 60 | 5–6 | General indoor, building structural tubes |
| ZM90 | 90 | 80 | 6–8 | Mild outdoor, packaging steel coils |
| ZM100 | 100 | 85 | 7–8 | General outdoor projects, structural steel |
| ZM120 | 120 | 100 | 8–10 | Factory fence tubes, ordinary outdoor steel sheets |
| ZM150 | 150 | 130 | 10–12 | General structural coils, outdoor engineering |
| ZM175 | 175 | 150 | 12–14 | Humid areas, landscape engineering |
| ZM200 | 200 | 170 | 14–16 | Agricultural greenhouse tubes, medium corrosion protection projects |
| ZM275 | 275 | 230 | 20–22 | Areas characterized by coastal locations, high rainfall, and high salt spray concentrations. |
Note: The “typical single-side thickness” in the table is estimated by formula: Total double-side weight ÷ 2 ÷ 6.6.
Common ZAM Coating Standards
| Standard | Description | Typical Coating Weight |
|---|---|---|
| JIS G 3323 | Japanese Standard for Zn-Al-Mg coated steel sheets | ZAM 120–300 g/m² |
| EN 10346 | European Standard for continuously hot-dip coated steel flat products | ZM 100–300 g/m² |
| ASTM A1046 | US Standard for Zn-Al-Mg alloy coated steel sheets | By grade |
| AS/NZS 4759 | Australian / New Zealand Standard | ZM 100–450 g/m² |
Coating Parameter Differences among ZAM Tubes, Coils and Sheets
Coating weight definition: ZM grade marking for ZAM coating refers to total double-side coating weight per square meter of steel surface. It is the core authoritative indicator for customs inspection and project acceptance.
Under the same ZM grade standard, the theoretical coating thickness and weight parameters of ZAM pipes, coils, and sheets are fully identical. Minor discrepancies only come from forming processes:
- ZAM Steel Coils: Flat substrate with highly uniform and stable coating. Highest parameter accuracy; raw material for cut sheets and tube fabrication.
- ZAM Steel Sheets: Cut from standard ZAM coils, fully matching original mill coating specs without performance loss.
- ZAM Steel Tubes: Roll-formed and welded from ZAM sheets. No coating damage on weld seams; overall anti-corrosion performance consistent with parent material.
How to Select ZAM Coating for Your Project
1. Quick Selection by Service Conditions
| Operating Environment | Recommended Grade | Application Scenarios |
|---|---|---|
| Dry indoor environment | ZM60–ZM120 | Indoor structural tubes, equipment support sheets, packaging steel coils |
| General outdoor environment | ZM150–ZM175 | Outdoor fencing, building cladding, agricultural facilities, best cost-performance |
| Severe coastal environment | ZM275 | Salt-spray resistance, rain erosion resistance, high-temperature oxidation resistance; outdoor service life up to 15–20 years |
2. Selection by ISO 9223 Corrosion Classes
Step 1: Determine Corrosion Class
| Class | Corrosivity | Typical Environment |
|---|---|---|
| C1 | Very low | Heated indoor spaces |
| C2 | Low | Rural areas, low pollution |
| C3 | Medium | Urban areas, moderate pollution |
| C4 | High | Industrial zones, coastal areas |
| C5 | Very high | Heavy industry, heavy salt spray |
| CX | Extreme | Offshore, tropical marine atmosphere |
Step 2: Select Coating Weight
| Corrosion Class | Recommended ZAM Coating |
|---|---|
| C1–C2 | ZAM 100–150 |
| C3 | ZAM 150–200 |
| C4 | ZAM 200–275 |
| C5 | ZAM 275–400 |
| CX | ZAM 400+ |
Step 3: Confirm with Supplier
- Coating composition (Zn/Al/Mg ratio)
- Coating weight standard (JIS, EN, ASTM)
- Single-side or double-side calculation
- Adhesion and bend test results
Comparison: ZAM Coating vs Hot-Dip Galvanized & Al-Zn Coating
| Coating Type | Common Grades | Salt Spray Hours | Outdoor Service Life | Core Advantages |
|---|---|---|---|---|
| Hot-Dip Galvanized | Z120-Z275 | 500–800 h | 3–5 years | Low procurement cost |
| Al-Zn Coating (AZ) | AZ150 | 1000–1500 h | 8–10 years | Excellent heat resistance |
| ZAM Zn-Al-Mg Alloy Coating | ZM275 | 2000–3000+ h | 15–20 years | Self-healing property, superior anti-corrosion, cut-edge rust resistance |
FAQ
Q: What is the difference between ZAM coating and ordinary galvanizing?
A: ZAM coating adds aluminum and magnesium to zinc. Magnesium greatly improves corrosion resistance, especially on cut edges and scratched areas, where conventional galvanized steel tends to fail first.
Q: How to convert ZAM coating thickness to weight?
A: Coating thickness (µm) multiplied by 6.6 equals coating weight (g/m²). For example, 30 µm ZAM coating equals approx. 198 g/m².
Q: Is ZAM coating suitable for coastal areas?
A: Highly suitable for coastal and heavy salt-spray environments. ZAM 275 or higher grade is recommended for C5 corrosion class.
Q: Can ZAM-coated steel tubes be welded?
A: Yes, conventional welding methods are applicable. However, coating will be damaged at weld zones. Zinc-rich repair paint is required for weld restoration.
Q: What standards apply to ZAM coating?
A: Main standards include JIS G 3323 (Japan), EN 10346 (Europe), ASTM A1046 (USA), AS/NZS 4759 (Australia & New Zealand).
Q: Which ZAM grades are most commonly imported?
A: ZM150 and ZM275 are mainstream export grades. ZM150 for general civil engineering and fencing projects; ZM275 is high-grade anti-corrosion option preferred for coastal, humid regions and premium industrial projects.
Get Quotation for ZAM Coated Steel Tubes / Coils / Sheets
We supply full range of ZAM steel tubes, ZAM steel coils and ZAM steel sheets. Customization is available for ZM coating grades, base metal thickness, product dimensions and export packaging.
Our technical team can assist you to select the proper ZAM coating grade according to project corrosion class and expected service life.
