Color-coated stainless steel sheet

1. Definition and Material Composition

Color-Coated Steel Plate, also known as Color-Coated Steel Sheet, is a composite material made from cold-rolled steel, galvanized steel, or aluminum sheets coated with multiple layers of organic paints (such as epoxy resin, polyurethane, and fluorocarbon resins) and cured at high temperatures. Its core features includeIntegrated corrosion resistance, decoration, and functionalityWidely used in construction, home appliances, automotive, and industrial packaging.

II. Core Manufacturing Processes

1. Substrate Pre-treatment

• Clean: Use alkaline degreasing (pH 12~14) to remove surface oils and oxide layers.

• Passivation: Phosphoric acid or chromate treatment (Cr⁶⁺ content ≤ 0.01%) to improve coating adhesion.

• Coating application process

  • Primer: Epoxy resin (high corrosion resistance, adhesion ≥5 MPa).

  • Intermediate Coat: Polyurethane (filled with micropores to enhance weather resistance).

  • Topcoat: Fluorocarbon resin (UV-resistant, temperature range -40 to 200°C).

  • Roll coatingCoating viscosity: 20~50 μm; application uniformity: ±10%.

  • Spray coatingAtomization pressure: 0.3~{1.6} MPa; film thickness control accuracy: 10~30 μm.

  • Coating Method：

  • Coating Systems：

• Bake and cure

  • Temperature gradient: 180~250°C staged baking, cure time 3~15 minutes, ensure coating crosslink density ≥ 90%.

• Post-processing

  • Film Thickness Inspection: Ellipsometry method (accuracy ±1 μm).

  • Pencil Hardness: ≥2H (GB/T 9278).

  • CoolCool slowly below 50°C to prevent coating cracking.

  • Quality Inspection：

III. Performance Metrics

1. Corrosion Resistance

• Soak in 10% H₂SO₄ solution for 24 hours; mass loss < 0.5%.

• Soak in 5% NaOH solution for 24 hours; mass loss < 0.3%.

• Salt Spray Test(ASTM B117): No red rust for >1000 hours (Class 10).

• Acid and alkali resistant(GB/T 1771):

• Mechanical Properties

  • Tensile Strength: ≥340MPa (substrate is cold-rolled steel SPCC).

  • Bending stiffness: EI = E×I (E=200 GPa, I is the moment of inertia).

  • Impact Toughness: Charpy V-notch impact value ≥ 45J at -20°C.

• Decorative Metrics

  • Color Difference Control: ΔE ≤ 1.5 (CIE Lab standard, GB/T 12967-2008).

  • GlossGloss ≥ 85GU, Matte ≤ 20GU.

  • Surface Texture: Offers customizable finishes, including matte, embossed, and metallic effects.

• Durability

  • QUV Aging(GB/T 18950): >2000 hours, Δb* ≤ 3%.

  • Temperature ResistanceNo color change or peeling after prolonged exposure to high temperatures of 150°C (fluorocarbon coating).

4. Typical Application Areas

1. Construction Industry

• Exterior Insulation Board: Combines rock wool/polyurethane with thermal conductivity ≤ 0.045W/(m K, meeting energy efficiency standards (GB/T 50185).

• Roof Corrugated Sheet: Thickness 0.4~1.2mm, wind pressure resistance ≥ 4kPa/m² (GB/T 25975).

• Home Appliance Manufacturing

  • Refrigerator / Washing Machine Panel:0.3~0.6mm color-coated steel, fingerprint-resistant (contact angle > 90°), RoHS compliant.

• Automotive Industry

  • Body panels: Three-coat system (primer + basecoat + clearcoat), chip resistance ≥ 1500 cycles (ASTM D3123).

• Industrial Packaging

  • Container side panel: Double-sided color-coated steel (corrosion-resistant on both sides), service life ≥ 10 years.

5. Selection and Quality Control

1. Substrate Selection

• For Construction: Prioritize hot-dip galvanized steel substrate (zinc coating ≥ 80 g/m², ASTM A123).

• Home Appliances: Cold-rolled steel SPCC (thickness ≥ 0.35mm).

• Paint Type

  • Outdoor Weather-Resistant: Fluorocarbon resin (PVDF content ≥ 30%).

  • Interior Decor: Polyurethane coatings (low cost, easy to clean).

• Certification Standards

  • GB/T 12754 (Classification and Technical Requirements for Color-Coated Sheets).

  • GB/T 12755 (Color-Coated Coil Dimensional Tolerances).

  • USA: ASTM D2378 (coating adhesion).

  • EU: EN 10157 (weather resistance).

With its superior comprehensive performance, color-coated coil has become a core material in modern industry and construction. Through technological innovation and green transformation, its application is expanding into high-end sectors such as new energy and aerospace.