Prepainted Steel Specifications & Standards
Prepainted Steel Overview
Pre-painted (coil-coated) metal is produced through a continuous coating process where both sides of the metal strip are cleaned, pretreated, coated, and oven-cured. The result is a uniform, durable, and ready-to-form material used in roofing, panels, appliances, and architectural cladding.
Prepainted steel mainly includes prepainted galvanized steel and prepainted galvalume steel. Learn more about prepainted steel in detail.
1. Typical Substrate Grades
| Base Metal | Standard | Coating Type | Typical Use |
|---|---|---|---|
| Cold Rolled Steel | ASTM A1008 / EN 10130 | Uncoated base for indoor use | Furniture, interior panels |
| Galvanized Steel (GI) | ASTM A653 / EN 10346 | Zinc coating (Z100–Z275) | Roofing, wall cladding |
| Galvalume (AZ) | ASTM A792 / EN 10346 | Al-Zn alloy coating (AZ100–AZ150) | Industrial roofing, appliances |
| Aluminum Alloy | EN AW-3003 / 5052 | Mill finish | Facade, ceilings, decorative use |
2. Coating System and Thickness
| Layer | Function | Material Type | Typical Thickness (μm) |
|---|---|---|---|
| Primer | Adhesion, corrosion protection | Epoxy / Polyester | 5–7 |
| Topcoat | Color, gloss, UV resistance | PE, SMP, PVDF | 15–25 |
| Backcoat | Protection, lubrication | Epoxy / Polyester | 5–10 |
| Total coating thickness | — | — | 25–40 (both sides combined) |
3. Coil Coating Process Parameters
| Process Step | Description | Typical Range |
|---|---|---|
| Line Speed | Continuous coating line speed | 60–180 m/min |
| Curing Temperature | Oven curing for polymerization | 220–260 °C |
| Oven Dwell Time | Exposure time | 20–40 s |
| Coating Adhesion | T-bend test | ≤ 3T (no cracking) |
4. Relevant Standards
| Standard | Description |
|---|---|
| EN 10169 | Continuously organic coated steel flat products |
| EN 13523 series | Test methods for coil coated metals (adhesion, bending, impact, salt spray) |
| ASTM A755 / A755M | Prepainted metallic-coated steel sheet for building panels |
| JIS G3312 | Prepainted hot-dip zinc-coated steel sheet |
| ISO 7724 / 2813 | Color and gloss measurement standards |
5. Common Performance Requirements
| Property | Test Method | Requirement (Typical) |
|---|---|---|
| Adhesion | EN 13523-7 | No peeling after cross-cut |
| Flexibility (T-bend) | EN 13523-7 | ≤ 3T, no cracks |
| Impact Resistance | EN 13523-5 | No cracking at ≥10 J |
| Salt Spray Resistance | EN 13523-8 | ≥ 500 h without red rust |
| Gloss Retention | ASTM D523 | >85% after 1000 h UV exposure |
| Color Difference | ΔE (CIE Lab*) | ≤ 1.0 after aging test |
6. Coating Options by Application
| Application | Recommended Coating | Topcoat Type | Color Range |
|---|---|---|---|
| Roofing & Wall Panels | High UV resistance | PVDF / SMP | RAL / custom |
| Household Appliances | Smooth & glossy | PE / Epoxy | White / Metallic |
| Industrial Enclosures | Chemical resistance | Epoxy-polyester | Grey / Blue |
| Decorative & Interior | High gloss / texture | Polyester | Full RAL range |
7. Packaging & Supply Conditions
Coil ID: 508 mm / 610 mm
Coil Weight: up to 10 tons
Width: 600–1500 mm
Delivery: coils or cut-to-length sheets
Protective film available on request
8. Quality Assurance
ISO 9001 / ISO 14001 Certified Production Lines
Each batch tested per EN 13523 methods
Material Test Certificate (MTC) available upon request