Wood grain color-coated board

I. Definition and Material Composition

Color-coated steel plates, also known as colored steel sheets, are composite materials made by coating cold-rolled steel, hot-dip galvanized steel, or aluminum plates with multiple layers of organic coatings (such as epoxy resin, polyurethane, and fluorocarbon resin). These coatings are cured through high-temperature baking to achieve corrosion resistance, decorative properties, and functional integration. They are widely used in construction, home appliances, automotive, and industrial packaging sectors.

II. Core Production Technologies

1. Substrate Pretreatment

• Cleaning: Alkaline degreasing (pH 12–14) to remove surface oil and oxidation layers.

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

• Coating Application Process

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

• Intermediate Coat: Polyurethane (fills micro-pores for improved weatherability).

• Top Coat: Fluorocarbon resin (UV resistance, temperature tolerance -40–200℃).

• Roll Coating: Apply coatings with viscosity 20–50μm, ensuring uniformity within ±10%.

• Spraying: Use atomizing pressure (0.3–0.6MPa) to control film thickness between 10–30μm.

• Coating Methods:

• Coating Systems:

• Curing Process

• Temperature Gradient: Bake at 180–250°C in stages for 3–15 minutes to ensure cross-linking density ≥90%.

• Post-Treatment

• Film Thickness: Ellipsometry measurement (precision ±1μm).

• Pencil Hardness: ≥2H (GB/T 9278).

• Cooling: Slow cooling to below 50°C to prevent coating cracking.

• Quality Control:

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III. Performance Indicators

1. Corrosion Resistance

• 10% H₂SO₄ solution immersion (24h, mass loss <0.5%).

• 5% NaOH solution immersion (24h, mass loss <0.3%).

• Salt Spray Test (ASTM B117): >1000 hours without red rust (Class 10).

• Acid/Alkali Resistance (GB/T 1771):

• Mechanical Properties

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

• Bending Stiffness: EI = E×I (E=200GPa, I: section moment of inertia).

• Impact Toughness: Charpy V-notch impact value ≥45J (-20℃ environment).

• Decorative Properties

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

• Glossiness: High-gloss surface ≥85GU, matte finish ≤20GU.

• Surface Texture: Customizable effects such as matte, embossing, and metallic finish.

• Durability

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

• Heat Resistance: No discoloration or delamination at 150℃ (fluorocarbon coating).

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IV. Typical Applications

1. Construction Industry

• Insulated Wall Panels: Combined with rock wool/polyurethane (thermal conductivity ≤0.045W/(m·K)), meeting energy-saving standards (GB/T 50185).

• Roofing Corrugated Sheets: Thickness 0.4–1.2mm, wind resistance ≥4kPa/m² (GB/T 25975).

• Refrigerator/Washing Machine Panels: 0.3–0.6mm color-coated steel with fingerprint resistance (contact angle >90°), complying with RoHS standards.

• Vehicle Body Panels: Three-coat system (primer + base coat + clear coat), stone chip resistance ≥1500 times (ASTM D3123).

• Container Sides: Double-sided color-coated steel with corrosion resistance, lifespan ≥10 years.

V. Selection and Quality Control

1. Substrate Choice

• Construction: Prefer hot-dip galvanized steel (zinc layer ≥80g/m², ASTM A123).

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

• Outdoor Applications: Fluorocarbon resin (PVDF content ≥30%).

• Indoor Decoration: Polyurethane coatings (cost-effective, easy to clean).

• GB/T 12754 (color-coated steel classification and technical requirements).

• GB/T 12755 (dimensional tolerances of color-coated steel).

• USA: ASTM D2378 (coating adhesion).

• Europe: EN 10157 (weatherability).

Color-coated steel plates have become an indispensable material in modern industry and construction due to their superior performance. Through technological innovation and green transformation, their applications will continue to expand into new fields such as new energy and aerospace.