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Help CenterSteel Coil & Strip & Color Coated Steel Coil，DX51D+Z、DX52D+Z、DX53D+Z、DX54D+Z、DX51D+AZ、S350GD+AZ
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1. Basic Product Definition
Color Coated Coil, also named prepainted steel coil, abbreviated as PPGI (Prepainted Galvanized Iron Coil) or PPGL (Prepainted Galvalume Coil).It takes cold rolled coil, hot-dip galvanized steel coil (GI), galvalume steel coil (GL) or electro-galvanized coil as base substrate.
Coating Layer Cross Section
It integrates anti-corrosion, weather resistance and decorative performance. All painting is finished in factory, no on-site spraying required; paint film keeps intact during bending, roll forming and stamping. It is the core deep-processing material widely used in construction, home appliances, transportation and decoration industries.
Core Layer Structure (From inside to outside)
Base steel substrate (CR/GI/GL)
Metallic anti-rust coating (zinc / aluminum-zinc alloy)
Chemical conversion passivation film (improve paint adhesion)
Epoxy primer
Color topcoat (weather-resistant main layer)
Back coating (protective paint for coil reverse side)Optional: PE protective film (anti-scratch for processing)
2. Complete Production Flow
Uncoiling & welding: Joint two coils for continuous production
Tension looper buffer: Stable production speed
Degreasing & multi-stage water cleaning: Remove oil, dust and surface impurities
Hot air drying: Eliminate residual moisture
Chemical conversion passivation: Form compact anti-corrosion film
Secondary drying
Primer roller coating + high-temperature baking
Topcoat roller coating + curing oven baking (core process)
Air cooling / water cooling
Optional lamination of PE protective film
Edge trimming & surface online inspection
Final coiling, marking, strapping and packaging
Common Coating Process Types
1-coat 1-bake (1/1): Single primer, low cost, only for indoor inner parts
2-coat 1-bake (2/1): Primer + single topcoat, general indoor decoration
2-coat 2-bake (2/2): Primer + topcoat with two independent curing sections, mainstream outdoor architectural grade
3-coat 3-bake (3/3): Extra clear top coat, ultra-high weather resistance PVDF grade for coastal heavy corrosion environment
3. Product Dimension Parameters
Standard Size Range
Base metal thickness: 0.12 ~ 1.5 mm; mainstream stock: 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2 mm
Width: 600 ~ 1500 mm; common widths: 1000, 1200, 1250 mm
Coil inner diameter: 508 mm / 610 mm
Single coil weight: 3 ~ 15 tons
Tolerance: Strict thickness & width tolerance, consistent surface coating thickness
Coating Film Thickness Standard
Topcoat dry film: 15 ~ 27 μm (varies by paint system)
Back coat dry film: 5 ~ 10 μm
Zinc / Aluminum-Zinc Coating Weight (Substrate)
Hot-dip galvanized GI: Z30 ~ Z275 g/m² (both sides total)
Galvalume AZ (55%Al+43.5%Zn+1.5%Si): AZ50 ~ AZ185 g/m²
4. Product Classification & Grades
4.1 Classified by Base Substrate
PPGI – Prepainted Hot-dip Galvanized CoilSubstrate: DX51D+Z / TDC51D+Z; low-medium corrosion resistance, general industrial & civil building
PPGL – Prepainted Galvalume CoilSubstrate: DX51D+AZ / TDC51D+AZ; superior heat & salt spray resistance, coastal, chemical plant, solar support
Prepainted Electro-galvanized Coil (PSECC)Thin zinc layer, smooth surface, mainly for home appliance interior parts
Prepainted Cold Rolled Coil (PCR)No metallic zinc layer, only indoor dry environment decoration
4.2 Classified by Paint Topcoat System (Core classification, different service life)
| Paint Type | Full Name | Weather Resistance | Service Life | Typical Application |
|---|---|---|---|---|
| PE | Polyester | Ordinary | 8–12 years | Indoor wall, temporary factory, simple roof |
| SMP | Silicone Modified Polyester | Medium | 12–18 years | Normal outdoor factory, warehouse, guardrail |
| HDP | High Durability Polyester | High | 18–25 years | Permanent industrial building, solar bracket |
| PVDF | Polyvinylidene Fluoride | Ultra-high | 25–30+ years | Coastal, chemical zone, high-end facade |
4.3 Classified by Mechanical Performance (Substrate Grade)
General forming grade: TDC51D+Z/AZ (simple bending, roofing tile)
Drawing grade: TDC52D+Z/AZ (medium stamping, door panel)
Deep drawing grade: TDC53D+Z/AZ (complex home appliance shell)
Structural high-strength grade: TS280GD / TS350GD / TS550GD (load-bearing purlin, structural support)
4.4 Classified by Surface Texture & Finish
Smooth solid color finish: RAL standard color system (white, grey, blue, red, green etc.)
Matte finish (low gloss 5–30°): Anti-fingerprint, high-end decoration
Embossed texture: Orange peel, leather grain, brick grain, wood grain
Metallic finish: Silver, golden metallic luster
Wrinkle finish, chalkboard finish, food-grade special coating
5. Advantages & Disadvantages
Main Advantages
Double anti-corrosion protection: Zinc metallic coating + organic paint film, far longer service life than bare galvanized steel
One-step finished product: Factory pre-painted, save post-processing spraying cost & labor
Rich color & texture options, stable color consistency in batch production
Excellent forming property: Paint film maintains adhesion after bending, roll forming, stamping without peeling or cracking
Light weight, high strength, easy installation, low maintenance cost
Wide thickness & paint grade selection to match different climate & corrosive environments
Limitations
PVDF high-performance grade has relatively high material cost
Sharp scratch will damage organic coating and cause local rust risk
Not suitable for long-term high-temperature environment above 120℃
Indoor PE grade will fade quickly under long-time strong UV exposure
6. Domestic & International Executive Standards
Chinese GB Standards
GB/T 12754-2019 Color Coated Steel Sheets and Strips (core national standard)
GB/T 13448 Test Methods for Color Coated Steel Sheets and Strips
GB/T 2518 Hot-dip galvanized steel strips
GB/T 14978 Hot-dip galvalume steel strips
International Standards
EN 10169 European prepainted steel standard
ASTM A755/A755M US standard for prepainted structural steel
JIS G3312 Japanese prepainted galvanized steel standard
ISO 9001 quality system certification; SGS salt spray & weather aging test certification
7. Main Application Industries
7.1 Construction Industry (Largest consumption)
Industrial plant roof & wall panel, steel structure warehouse, logistics park, livestock farm, prefab house, purlins, color steel tile, exterior curtain wall, garage door, fence, advertising billboard substrate, solar photovoltaic bracket, cold storage enclosure.
7.2 Home Appliance Manufacturing
Refrigerator backboard, washing machine shell, air conditioner outer casing, water heater housing, range hood, electrical distribution cabinet, decorative metal panel.
7.3 Transportation & Machinery
Truck carriage plate, container auxiliary decorative plate, agricultural machinery housing, mechanical equipment outer shell, traffic road sign.
7.4 Decoration & Light Industry
Indoor partition, metal ceiling, decorative wood grain plate, furniture metal parts, storage rack.
8. Mandatory Factory Inspection Items
Dimensional test: Base thickness, total width, coil weight, flatness
Coating test: Zinc coating weight, primer & topcoat dry film thickness
Mechanical test: Yield strength, tensile strength, cold bending test (no paint peeling after bending)
Coating performance test: Salt spray resistance, UV aging resistance, pencil hardness, adhesion cross-cut test
Visual inspection: Color difference, scratch, pinhole, missing coating, spot defect
Special grade extra test: Heat resistance, chemical solvent resistance
9. Packaging, Storage & Transportation Instructions
Packaging: Inner anti-rust waterproof paper, middle plastic film, outer steel strip circumferential strapping; inner & outer coil edges fitted with metal guard rings. Export goods adopt seaworthy reinforced wooden pallet packaging; PE protective film optional as customer request.
Storage: Store in dry & ventilated warehouse, avoid rain, dew and humid air to prevent coating blistering. Stack height limited to avoid coil deformation.
Transportation: Use special coil transport rack; adopt soft sling during lifting to prevent surface scratch and edge collision damage. Keep coil horizontal or vertical as marked “eye to sky” label.
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