Prepainted Steel Coil (PPGI & PPGL) Manufacturer & Supplier
Color Coated Steel Coils for Roofing Sheet, Roll Forming and Sandwich Panel Manufacturers.
Prepainted steel coils are manufactured using GI or GL substrates with a durable paint coating, making them ideal for roofing systems. Witop supports bulk procurement.
Durable Color Coating System๏ผ
Stable Substrate Quality๏ผConsistent Surface Finish๏ผ Wide Color & Thickness Options๏ผ B2B Supply & Inspection Support
Prepainted Steel Coil Technical Sheet
| Prepainted Steel Coil | ||
| Standard | JIS G 3312, EN 10169, ASTM A755 | |
| Grade | CGCC/CGCH,DX51D/DX52D | |
| Color | Clientโs Sample Color or Any Ral Colorย (Down Load RAL Color Chart) | |
| Painting Brand | Nippon, Akzo-Nobel, KCC | |
| Top Side Paintingย Film | Primer | 5-10ฮผm |
| Top Coating | 10โ25ฮผm | |
| Back Side Paintingย Film | Primer | 5-10ฮผm |
| Top Coating | 10โ25ฮผm | |
| Surface Treatment | PVC Film, Wrinkle/Matt, Printed, Embossed | |
| Thickness | 0.12-3.00MM | |
| Width | 20-1250MM | |
| Zincย Coating | 40-275G/M2 | |
| Hardness | Softy,ย Semiย Hard, Full Hard, G550 | |
| Coilย Weight | 3-5MT/Coilย orย Customized | |
| Coil Inner Diameter | 508MM or 610MM | |
| Package | Standard Seaworthyย Exportingย Packing | |
| MOQ | 25MT | |
| Capacity | 12500MT/Month | |
| Transportย Type | Vessel Container, Vessel Bulkย ,Railway Container,Railway Wagon | |
| Loadingย Port | Tianjin,ย Qingdao, Ningbo, Shanghai and other port | |
Prepainted Steel Coil Description
Prepainted Steel Coil Description introduces color coated steel manufactured with GI or GL substrates for durable roofing and cladding solutions. As a professional steel manufacturer and wholesale supplier, we provide PPGI and PPGL coils with PE, SMP , HDP and PVDF paint systems.
The consistent coating adhesion ensures smooth forming and aesthetic finish in roofing sheet production. Compared with raw galvanized steel, prepainted steel reduces additional painting costs and improves efficiency. Ideal for roofing makers, distributors and construction companies requiring stable bulk supply.
Prepainted Steel Coil Applications
Prepainted Steel Coil for Sandwich Panel Manufacturing
WITOP supplies prepainted steel coil for continuous sandwich panel production, supporting different insulation cores, panel structures and end-use requirements. Prepainted steel coil is designed for aesthetic and architectural applications, combining corrosion protection with decorative value.
Our Prepainted Steel coils can be used for:
- EPS Sandwich Panels โ Suitable for cost-effective wall and roof panel production.
- PU Sandwich Panels โ Suitable for insulated building panels requiring better thermal performance.
- PIR Sandwich Panels โ Suitable for higher fire-performance and thermal insulation requirements.
- Rock Wool Sandwich Panels โ Suitable for industrial and commercial buildings where fire resistance is a key consideration.
- Roof Sandwich Panels โ Designed for profiled exterior skins used in roofing systems.
- Wall Sandwich Panels โ Suitable for exterior and interior wall panel production.
- Cold Room Panels โ Suitable for insulated panels used in cold storage, refrigeration rooms and temperature-controlled facilities.
Recommended Specification for Sandwich Panel Production
The right Prepainted steel coil specification depends on your panel type, roll-forming line, panel profile and project requirements. Instead of selecting steel only by price, confirm the following parameters before ordering:
| Item | Recommended Specification |
|---|---|
| Thickness | Based on panel design and roll-forming requirements |
| Steel Grade | DX51D / Custom |
| Metallic Coating | Z coating / Aluzinc Coating / Custom |
| Paint System | PE / SMP / HDP/ Other coating systems |
| Color | RAL color / Customer sample |
| Width | Based on panel line and finished panel width |
| Surface | High gloss / Matt / Embossed / Custom |
| Coil Weight | Based on your decoiler and production line |
| Inner Diameter | 508 mm / 610 mm |
| Coil OD | Based on your production equipment |
How to Choose Prepainted steel coil for Your Sandwich Panel Line
For EPS, PU, PIR and rock wool sandwich panels, the substrate, metallic coating, paint system, thickness and coil width should be selected according to the panel structure and forming process.
If you manufacture both roof panels and wall panels, the required specifications may differ. Your panel profile, forming speed, insulation core, installation environment and target market should all be considered before placing an order.
Send us your panel thickness, finished width, profile drawing or production-line requirements, and WITOP can recommend a suitable PPGI coil specification for your application.
Residential Roofing Sheets
Popular in housing projects requiring color consistency.
Wall Cladding Systems
Used for exterior decorative panels and facades.
Sandwich Panel Production
Applied in insulated panel systems for warehouses and cold rooms.
Commercial Buildings & Retail Stores
Provides brand-matching RAL colors.
Modular & Prefabricated Houses
Enhances visual appeal while maintaining durability.
Prepinted Galvalume Steel Process Flow Chart
1. Pay Off
2. Welder
3. Entry Looper
4. Oil Degreasing
5. Dry Section
6. Primer Coating
8. Refined Coating
9. Dry Baking
10. Looper
11. Cutting
12. Finshed Products
Packing Details Standard export package
3 layers of packing, inner side is anti-water craft paper, PVC plastic film is the middle and outer side covered by at least 0.45mm thick steel sheet,wrapped by minimum seven steel strapping strips with lock catch.
In particular, WITOP steel places desiccant on the coil inner core side and on both lateral sides of the coil for bulk transportation to ensure that coils are delivered to clients in good condition.
Package can be customized as client’s requirements.
FAQ โ Prepainted Steel Coil
Coastal environments are saturated with chloride ions and high humidity. The aluminum in PPGL substrates forms a stable oxide film that blocks chloride penetration, while the zinc provides necessary cut-edge protection. Tests show its salt spray resistance is multiple times that of PPGI. Additionally, its high thermal reflectivity helps lower interior building temperatures in hot coastal regions.
The primary difference is the process. Prepainted steel is “pre-painted” then formed (continuous production line), resulting in a thin, uniform coating (typically 20-40 ฮผm) suitable for large-scale roll forming. Powder coating is usually “post-painted” after the metal is formed, resulting in a thicker coating (60-100 ฮผm) for individual, complex components.
Failure typically follows four stages:
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Loss of gloss and fading
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Chalking (a white powder forms on the surface)
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Micro-cracking and blistering
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Substrate rusting (red rust) Maintenance should ideally begin at the chalking stage to avoid the exponential repair costs associated with substrate rusting.
Grinders generate high-temperature sparks that char the organic coating. More critically, the flying hot metal shards (swarf) embed themselves into the paint. Within weeks, these shards rust, creating hundreds of tiny red spots (swarf staining) that destroy the anti-corrosion system of the entire panel.
It depends on your project’s timeframe. For temporary structures (5-10 years), PE is sufficient. However, for airports, landmarks, or long-term industrial plants, PVDF ensures no visible color shift for over 20 years. When considering the cost of scaffolding and labor for repainting, PVDF is actually the lowest-cost option in a 30-year lifecycle model.
These are high-corrosion zones. Choose a high-zinc or Zinc-Aluminum-Magnesium (ZAM) substrate with a thick Polyurethane (PU) or HDP coating. The backer coat is also critical; it should be thickened to prevent moisture from eroding the panel from the inside out.
Oil canning is a visual waviness or distortion in the flat areas of metal panels. It is typically caused by physical stresses (such as substrate thinness, improper roll forming, or over-tightened fasteners) rather than a chemical defect. It is an aesthetic issue and is not usually considered a basis for rejection in international standards.
The cut edge leaves the metal substrate exposed without paint protection. While the zinc layer sacrificially protects the edge, it is consumed much faster in salt-spray environments. Once the local protection is exhausted, corrosion spreads under the paint layer (delamination). Applying edge sealants is recommended for coastal buildings.
Key data includes:
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Substrate Grade (e.g., DX51D)
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Metallic Coating Weight (e.g., Z275 or AZ150)
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Coating Thickness (Top/Back)
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Paint Type (PE/PVDF)
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Physical Test Results (particularly T-bend and Pencil Hardness)
Telescoping (lateral layer shifting) is caused by uneven winding tension or severe lateral jolts. Ensure coils use steel or hard paper cores and are secured with wood frames. Always load coils with the eye parallel to the direction of travel and use high-strength strapping to maintain tension.
Many international buyers prefer direct manufacturers with long-term export experience.
