Do you really understand color coated steel coil products?

Color-coated steel coil PPGL PPGI is a steel product with a coated surface, which is widely used in construction, home appliances, transportation, and other fields. The following is the core knowledge sharing of the industry:
I. The basic composition of color-coated steel coils
1. Substrate type:
- Cold-rolled substrate: high surface flatness, suitable for fine processing.
- Hot-dip galvanized substrate (GI): strong corrosion resistance, often used as building exterior panels.
- Alu-zinc substrate (GL/GLH): better high-temperature resistance and corrosion resistance (the ratio of aluminum to zinc is usually 55% aluminum and 43.4% zinc).
- Electro-galvanized substrate (EG): uniform coating, mostly used for home appliance panels.
2. Coating materials:
- Primer: epoxy resin (strong adhesion), polyester resin (general purpose).
- Topcoat:
- Polyester (PE): low cost, medium weather resistance, suitable for indoor use.
- Silicon modified polyester (SMP): improved weather resistance, suitable for outdoor construction.
- Fluorocarbon (PVDF): UV-resistant and chemically resistant, with a service life of more than 20 years.
- High weather resistance (HDP): Performance is close to fluorocarbon but the cost is lower.
3. Coating process:
- Roller coating: mainstream process, coating on both sides (2/1 or 2/2 structure).
- Film thickness control: topcoat is usually 20-25μm, primer is 5-10μm.
2. Core performance indicators
1. Corrosion resistance:
- Salt spray test requirements: 500 hours in ordinary environment (such as polyester), more than 1000 hours in coastal areas (fluorocarbon).
- Cross-hatch method to test adhesion (0-1 level is excellent).
2. Mechanical properties:
- Hardness (pencil hardness ≥H), bending performance (0T-3T, T is the plate thickness).
- Processability: Erickson stamping test (≥6mm is good).
3. Weather resistance:
- QUV accelerated aging test: Fluorocarbon paint can last up to 2000 hours without powdering.
III. Application fields and material selection
Industry Typical uses, recommended substrate/coating, building roofs, walls (curtain walls), GL substrate + PVDF/SMP coating (outdoor), home appliances, refrigerators, air conditioning panels, EG substrate + PE coating (indoor anti-fingerprint treatment), transportation, compartment partitions, logistics boxes, GI substrate + HDP coating (wear-resistant and corrosion-resistant) furniture, office partitions, cabinets cold-rolled substrate + wood grain transfer decoration.
IV. Industry trends and innovations
1. Environmental protection technology:
- Chromium-free passivation (Cr-Free): replaces traditional hexavalent chromium passivation process.
- Water-based coatings: VOC emissions are reduced by more than 50%, but the drying energy consumption is high.
2. Functional coatings:
- Self-cleaning coatings (photocatalytic TiO₂), antibacterial coatings (silver ions).
- Heat insulation coatings (reflect infrared rays and reduce building energy consumption).
3. Intelligent manufacturing:
- Online defect detection (AI visual recognition of pinholes and scratches).
- Precision coating control (PID algorithm ±1μm error).
V. Key points of procurement and quality control
1. Key parameter verification:
- Zinc layer weight (such as GI board double-sided ≥60g/m²).
- Color difference (ΔE≤1.0, spectrophotometer detection required).
2. Common problems:
- Coating peeling: mostly due to incomplete pre-treatment (degreasing, insufficient phosphating).
- Color difference: caused by uneven baking temperature or differences in coating batches.
3. Standard system:
National standard (GB/T 12754), American standard (ASTM A755), European standard (EN 10169).
VI. Cost influencing factors
1. Substrate proportion: about 60%-70% of total cost (sensitive to zinc price fluctuations).
2. Coating cost: The price of fluorocarbon paint is 2-3 times that of polyester.
3. Influence of specifications: ultra-wide (＞1250mm), ultra-thin (＜0.2mm)
VII. Representative enterprises and markets
- Sharing by the world's leading factories:
- China: Baosteel, Ansteel, Shougang.
- International: Tata Steel (Europe), Posco (South Korea), Nippon Steel (Japan).