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What Is JIS G3312? Prepainted Galvanized Steel Standard
JIS G3312 is a Japanese Industrial Standard covering prepainted hot-dip galvanized steel sheets and coils (PPGI).
It specifies requirements for base steel quality, metallic coating mass, paint coating systems, dimensional tolerances, and product performance, ensuring consistent quality for coated steel used in construction and industrial applications.
JIS G3312 products are commonly used in roofing, wall cladding, appliances, and structural panels, and are often compared with ASTM A755 and EN 10169 in global trade.
Table of Contents
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1️⃣ Steel Grades and Base Materials1️⃣ Steel Grades and Base Materials
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2️⃣ Dimensions and Tolerances2️⃣ Dimensions and Tolerances
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3️⃣ Coating and Paint Systems3️⃣ Coating and Paint Systems
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4️⃣ Performance Requirements4️⃣ Performance Requirements
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5️⃣ Applications5️⃣ Applications
1️⃣ Steel Grades and Base Materials
JIS G3312 classifies products by strength level and forming capability, allowing selection for commercial, drawing, or structural use.
| Product Class | Base Steel | Typical Use |
|---|---|---|
| CGCC | SGCC / DX51D | General forming |
| CGCH | SGCH | Hard quality |
| CGCD1 | SGCD1 | Drawing quality |
| CGC340–570 | SGC340–SGC570 | Structural applications |
Base materials are typically produced in accordance with JIS G3302 before coating.
2️⃣ Dimensions and Tolerances
Typical Size Range
| Parameter | Range |
|---|---|
| Thickness | 0.12 – 3.0 mm (PPGI mainly 0.12 – 1.5 mm) |
| Width | 600 – 1500 mm |
| Coil ID | 508 / 610 mm |
Typical Tolerances
| Item | Tolerance |
|---|---|
| Thickness | ±0.02 – 0.05 mm |
| Width | ±5 – 10 mm |
| Length (sheets) | ±10 – 15 mm |
3️⃣ Coating and Paint Systems
Metallic Coating
| Coating Type | Coating Weight |
|---|---|
| Zinc (GI) | Z30 – Z275 g/m² |
| Al-Zn (AZ) | AZ30 – AZ150 g/m² |
Paint Coating Structure
| Layer | Thickness |
|---|---|
| Primer | 5 – 10 µm |
| Topcoat | 15 – 25 µm |
| Back coat | 5 – 10 µm |
Common paint systems include PE, SMP, HDP, and PVDF, selected based on exposure and durability requirements.
4️⃣ Performance Requirements
JIS G3312 verifies product quality through coating durability and forming performance tests.
| Test Item | Requirement |
|---|---|
| Adhesion | No peeling |
| Flexibility | No cracking at 2T–3T bend |
| Impact Resistance | ≥9 J |
| Salt Spray Resistance | ≥500 h |
| UV Resistance | Acceptable color change |
These properties ensure long-term performance in outdoor and industrial environments.
5️⃣ Applications
JIS G3312 prepainted galvanized steel is widely used for:
Roofing and wall cladding
Industrial buildings and warehouses
Appliances and metal enclosures
Transportation and container panels
Architectural components
Its balance of corrosion resistance, surface quality, and mechanical stability makes it suitable for both functional and decorative applications.
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