Color-coated coil: Functional coating coil manufactured on a large scale and continuously

In automated production lines for sectors like construction, home appliances, and transportation, color-coated coils, with their core advantages of continuous roll-feeding and coating functionality, offer a highly efficient alternative to conventional steel coils with post-painting. Using cold-rolled, galvanized, or stainless steel coils as substrates, they undergo continuous degreasing, phosphating, roller-coating of a colored organic coating (primer and topcoat), and high-temperature curing before being directly wound into coils. While inheriting the mechanical properties of the substrate and the continuous processing characteristics of the coil, the coating eliminates the need for secondary coating, offers corrosion resistance, and allows for multi-color customization. Suitable for a wide range of applications, including continuous forming of architectural color-coated steel sheets, batch stamping of appliance housings, and automated container welding, color-coated coils are key materials that balance efficiency and functionality in industrial-scale production. I. Basic Concepts and Core Components of Color-Coated Coil
The essence of color-coated coil is a composite structure of "rolled substrate + continuous coating." Its core value lies in its "continuous coating process + roll form." It addresses the pain points of conventional steel coils, such as the need for offline painting, low efficiency, and uneven coating. It also overcomes the limitations of color-coated sheets, such as single-sheet feeding and difficulty adapting to continuous production lines. Its core components include two parts:

(I) Substrate: Determines Basic Performance and Application Scenario

The substrate is the "skeleton" of the color-coated coil, directly affecting the coil's strength, corrosion resistance, and processing suitability. The mainstream types are similar to those of color-coated sheet substrates, but place greater emphasis on "coil stability" (to prevent deviation and cracking during rolling):

Cold-rolled substrate coil: Based on cold-rolled steel coil (thickness 0.15-2.0mm, coil weight 10-30 tons), it features a smooth surface and high dimensional accuracy (thickness tolerance ±0.01mm), but weak corrosion resistance (no rust-proof coating) and is only suitable for indoor continuous processing (such as appliance backplane stamping). A thick coating is required to enhance weather resistance.

Galvanized substrate coil: Based on hot-dip galvanized steel coil (GI) or electrogalvanized steel coil (EG), the zinc content is 50-275g/㎡ (hot-dip galvanizing) or 10-20g/㎡ (electrogalvanizing). The coil width 1000-1250mm (suitable for mainstream production lines), with excellent basic corrosion resistance, is the mainstay for outdoor applications (such as architectural color steel sheet forming).
Stainless steel substrate coils: Based on 304/430 stainless steel coils, they offer the highest corrosion resistance, but are more expensive (3-5 times that of galvanized substrate coils). Coil weights are typically ≤20 tons (to avoid damage to production lines due to excessive weight), and are only used in high-end applications (such as continuous cutting of medical device casings). The coating primarily serves decorative and fingerprint-resistant functions.
Specialty substrate coils: These include galvanized steel coils (55% aluminum, 43.4% zinc, and 1.6% silicon) and aluminum coils. The former offers superior weather resistance to galvanized coils (12-15 years outdoor life) and is suitable for highly weather-resistant construction applications. The latter is lightweight (density 2.7g/cm³) and is used for lightweight continuous processing (such as rolling RV casings). (II) Coating: Imparting Functionality and Decorative Features (Features of a Continuous Process)
The coating is the outer layer of the color-coated coil. It utilizes a continuous roller coating process (as opposed to the single-sheet coating of color-coated sheet). Multiple sets of rollers operate simultaneously, achieving both uniformity and efficiency. The typical coating structure is "primer + topcoat + backcoat" (the backcoat prevents corrosion within the coil):

Primer: 5-10μm thick. After continuous application, it is dried at 180-220°C to enhance adhesion between the substrate and the topcoat (adhesion ≥ 5MPa). Epoxy resin (excellent corrosion resistance) and polyester resin (low cost) are commonly used.

Topcoat: 15-25μm thick. It is categorized into three functional categories, all using a continuous color matching system to achieve color consistency (color difference ΔE ≤ 1):

Polyester (PE): Cost-effective, moderate weather resistance (5-8 years of outdoor life), suitable for home appliances and general construction.

PVDF: Excellent weather resistance (15-20 years of outdoor life), UV resistance. Acid and alkali resistant, suitable for high-rise buildings and marine environments.
Silicon-modified polyester (SMP): Weather resistance of 8-12 years, high hardness (pencil hardness ≥ 2H), and scratch resistance, suitable for roof panels and traffic signs.
Textured coating: Through simultaneous processing with continuous embossing rollers, wood, stone, and brushed textures (texture depth 0.1-0.3mm) are achieved, eliminating the need for subsequent secondary embossing and making it suitable for continuous molding of interior walls in integrated housing.
Key specifications for color-coated coils: Thickness 0.15-2.0mm (mainstream 0.3-0.8mm), coil width 1000-2000mm (customizable to suit production lines), coil weight 10-30 tons (standard 20 tons, compatible with automated unwinders), and lengths up to 1000-2000 meters (a single coil can meet daily continuous production needs).

II. Core Classification of Color-Coated Coil (By Substrate and Function)

The classification logic for color-coated coils revolves around "substrate type" and "coating function," combined with "suitability for continuous processing" to establish clear application boundaries:

(I) Classification by Substrate Type (Basic Dimension)

Cold-Rolled Substrate Color-Coated Coil

Features: High surface flatness (Ra ≤ 0.4μm), coil weight of 15-25 tons, suitable for high-precision continuous stamping (to avoid coating cracking), but weak corrosion resistance, requiring indoor storage.

Applications: Continuous stamping of home appliance casings (such as refrigerator side panels and washing machine back panels, with daily production capacity exceeding 100,000 pieces), continuous cutting of interior furniture panels (such as cabinet door panels). The coating is primarily PE (low cost and meets indoor weathering requirements). Galvanized-Based Color-Coated Coil (Approximately 75%)

The main categories of color-coated coil are divided into two categories:

Hot-Dip Galvanized (GI) Color-Coated Coil: The zinc layer is thick (50-275g/㎡), highly corrosion-resistant, and has a coil weight of 20-30 tons. It is suitable for continuous forming of architectural color-coated steel sheets (such as factory wall panels and roof panels).

Electrogalvanized (EG) Color-Coated Coil: The zinc layer is thin (10-20g/㎡), with a smoother surface (Ra ≤ 0.2μm). The coil weight is 10-20 tons. It is suitable for continuous stamping of high-end home appliance housings (such as air conditioner outer casings and microwave oven panels).

Applications: Outdoor construction (65%), home appliance manufacturing (25%), and transportation facilities (10%). The coatings are primarily PE (for general applications) and SMP (for high-weather resistance applications). Stainless Steel Coated Coil

Features: Extremely corrosion-resistant (rust-proof substrate), coil weight ≤ 20 tons (to avoid overloading the production line), coating only for decorative/fingerprint protection, high price.

Applications: Continuous cutting of medical device housings (such as sterile cabinet panels), continuous molding of offshore platform decorative panels (salt spray resistant), and continuous lamination of high-end commercial space walls (such as department store counters). Coatings primarily include PVDF (weather-resistant) and antibacterial resins (medical).

Specialty Coated Coil

Galvalume Coil: Weather resistance surpasses GI coil (12-15 years outdoor use), coil weight 20-25 tons, suitable for continuous molding of roof panels for large venues (such as stadiums and airport terminals).

Aluminum Coated Coil: Lightweight (60% lighter than steel coil), coil weight 10-15 tons, suitable for continuous rolling of RV housings and continuous cutting of aircraft interiors (for lightweighting needs). (II) Classification by Coating Function (Application Dimension)
Weather-Resistant Color-Coated Coil
Coating: PVDF or SMP resin with added UV absorber. Weather resistance after continuous coating: ≥8 years (SMP) or ≥15 years (PVDF). Color difference ΔE ≤ 2 at any position within the roll (ensuring batch consistency).

Applications: Continuous forming of high-rise building curtain walls (e.g., PVDF color-coated coil used for the Shanghai Tower exterior), continuous processing of color-coated steel sheets for factories in coastal areas (salt spray resistant), and continuous cutting of outdoor billboards (maintenance-free). Functional Color-Coated Coil

Designed for specific scenarios, this product meets multiple requirements through continuous functional coating:

Antibacterial Color-Coated Coil: The coating incorporates silver ions, achieving an antibacterial rate of ≥99% (against E. coli) after continuous coating. Suitable for continuous molding of food factory wall panels and continuous stamping of hospital furniture.

Self-Cleaning Color-Coated Coil: The coating contains nano-TiO₂, achieving a contact angle of ≥110° after continuous lamination (self-cleaning in rainwater). Suitable for continuous molding of high-rise building exterior walls and continuous cutting of photovoltaic panel backsheets.

Thermal Insulation Color-Coated Coil: The coating incorporates hollow microspheres, achieving a solar reflectance of ≥80% after continuous coating. Suitable for continuous molding of factory roof panels (reducing temperatures by 3-5°C in summer) and continuous processing of prefabricated housing wall panels.

Decorative Color-Coated Coil

Coating: Available in PE or matte PVDF, continuous embossing rollers create wood, stone, and brushed metal textures (with a texture consistency of ≥95%), eliminating the need for post-processing. Applications: Continuous forming of interior walls in integrated housing (wood-grain coils, eliminating the need for wallpaper after installation), continuous cutting at shopping mall counters (brushed metal coils), and continuous stamping of furniture door panels (stone-grain coils).

III. Key Performance Advantages of Color-Coated Coil (Comparison of Color-Coated Sheet and Ordinary Steel Coil)
The performance advantages of color-coated coils lie in the combined advantages of continuous coil processing and coating functionality, precisely addressing the pain points of large-scale production:

Continuous Processing Efficiency: From "Single-Sheet Loading" to "Unmanned Feeding"

Ordinary steel coils must be cut into sheets before being painted offline (efficiency ≤ 500 m2/day), while color-coated sheets require manual single-sheet loading (efficiency ≤ 1,000 m2/day). Color-coated coils can be continuously fed through automated unwinders (speeds of 10-20 m/minute, with a daily production capacity of ≥ 12,000 m2), making them suitable for continuous production lines such as stamping, forming, and welding. For example, a home appliance factory uses EG-based color-coated coils to produce refrigerator side panels, with a daily production capacity of up to 20,000 units, double the capacity of color-coated sheets.

Material Utilization: From "Scrap" to "Zero Waste in Fixed Lengths"

When cutting color-coated sheets, the scrap rate is ≥10% (for example, a 1.2m-wide wall panel requires cutting a 1.5m-wide sheet). Color-coated coils can be customized to the width of downstream products (for example, a 1.2m-wide wall panel requires a 1.2m-wide color-coated coil), resulting in a material utilization rate of ≥98%. Furthermore, roll-feeding eliminates individual sheet seams (for example, continuous forming of architectural color-coated steel sheets results in seamless, improved waterproofing). Coating Consistency: From "Batch Variation" to "Intra-Roll Uniformity"

Offline painting of ordinary steel coils is prone to color variation (ΔE ≥ 3 between batches) and uneven coating thickness (±5μm). Color-coated coils, produced using a continuous roller coating process, achieve an intra-roll coating thickness tolerance of ±1μm and a color variation ΔE ≤ 1, ensuring uniform appearance across batches. For example, a container factory using GI-based PE color-coated coils can produce 50 container side panels with no noticeable color variation from a single roll, meeting international shipping appearance standards. Storage and Transportation Costs: From "Large Space" to "High Efficiency and Intensive Use"

A 20-ton color-coated sheet of the same weight occupies approximately 20 square meters (stacked individually), while a 20-ton color-coated coil occupies only 3 square meters (coiled cylindrically), reducing storage costs by 85%. During transportation, color-coated coils can be loaded in batches on dedicated coil transporters (30 coils per vehicle, approximately 600 tons), resulting in a 40% lower transportation cost than color-coated sheets (which require wooden crating, with 500 sheets per vehicle, approximately 50 tons).

IV. Key Application Areas of Color-Coated Coil (Large-Scale Continuous Manufacturing Scenarios)

The "continuous feeding + functional coating" characteristics of color-coated coils make them a dominant force in mass production applications. The core applications are as follows:

(I) Construction (approximately 65%)

Industrial factory color-coated steel sheets: GI-based PE color-coated coils (0.3-0.5mm, roll weight 20 tons) are processed into C-shaped steel wall panels/roof panels using a continuous forming machine (daily production capacity of 10,000 square meters). They are weather-resistant for 5-8 years and require no nailing for installation (interlocking connections). For example, blue PE color-coated coils are used in automotive factories; a single roll can cover a 1,000 square meter roof.

Prefabricated houses: GI-based wood-grain/stone-grain color-coated coils (0.4-0.6mm) are continuously formed into interior and exterior wall panels (daily production capacity of 5,000 square meters). These panels are prefabricated in factories and assembled on-site (reducing construction time by 50%). For example, prefabricated houses for post-disaster resettlement sites can be built with just three rolls of color-coated coils. 10 houses;
High-rise building curtain walls: PVDF color-coated rolls (0.6-0.8mm) on a galvanized substrate are continuously cut into curtain wall panels (daily production capacity: 3,000 square meters). They are weather-resistant for 15-20 years and UV-resistant (no fading). For example, the buildings surrounding the Canton Tower use silver-gray PVDF color-coated rolls. Curtain wall panels processed from single rolls have no visual difference. (II) Home Appliances (approximately 20%)

White appliance housings: EG substrate PE color-coated coils (0.3-0.5mm, coil weight 15 tons) are continuously stamped into refrigerator side panels and washing machine back panels (daily production capacity 20,000 pieces). They feature a smooth surface (suitable for logo printing) and are scratch-resistant (hardness ≥ 2H).

Black appliance parts: Matte PE color-coated coils (0.4mm) are continuously cut into TV back panels and microwave oven housings (daily production capacity 15,000 pieces). They are fingerprint-resistant (surface resistance 10⁸-10¹⁰Ω).

Small appliance housings: Cold-rolled substrate thin-gauge color-coated coils (0.15-0.2mm) are continuously stamped into rice cooker housings and electric kettle bases (daily production capacity 50,000 pieces). They are lightweight (10% lighter than ordinary steel coils). (III) Transportation and Logistics (approximately 10%)

Containers: Wear-resistant PE color-coated coils (0.8-1.2mm thick, 25 tons coil weight) on GI substrates are continuously welded into container side panels/roof panels (daily production capacity: 50 containers). They are impact-resistant (impact strength ≥ 20kJ/m²) and seawater corrosion-resistant (rust-free after 5 years of sea transport).

RVs and Special Vehicles: Color-coated aluminum substrate coils (0.5mm thick, 10 tons coil weight) are continuously rolled into RV hulls (daily production capacity: 30 RVs). They are lightweight (60% lighter than steel coils) and offer excellent thermal conductivity (insulating heat).

Traffic Signs: Highly reflective color-coated coils (0.4mm thick) are continuously cut into road signs (daily production capacity: 1,000 pieces). They feature a reflectivity ≥ 70% (visible at night up to 300 meters) and are weather-resistant for 8 years. (IV) Other Sectors (Approximately 5%)

Food Factories/Hospitals: Antibacterial color-coated coils (0.5mm) are continuously formed into workshop wall panels (daily production capacity: 2,000 square meters), with an antibacterial rate of ≥99% and easy cleaning.

Photovoltaic Support: Self-cleaning color-coated coils (0.5mm) are continuously cut into photovoltaic panel backsheets (daily production capacity: 10,000 panels), with rainwater self-cleaning, improving photovoltaic efficiency.

Furniture Manufacturing: Cold-rolled wood-grain color-coated coils (0.3-0.4mm) are continuously stamped into cabinet door panels (daily production capacity: 3,000 pieces), eliminating the need for veneer and resisting mildew.
V. Future Development Trends of Color-Coated Coil

With the upgrade of automated manufacturing and the advancement of the "dual carbon" goals, color-coated coils are developing towards "environmental protection, functional integration, customization, and intelligence":

Environmental Protection: Low-VOC Coatings and Recycling

Replacing traditional solvent-based coatings with solvent-free powder coatings (VOC emissions ≤ 10g/L) and water-based coatings (soluble in water, odorless), compliant with EU REACH and China GB 18581 standards; establishing a color-coated coil recycling system where waste coils can be separated from the substrate (coatings are incinerated at high temperatures, with a recycling rate of ≥90%) and re-rolled into new coils, reducing solid waste pollution.

Functional Integration: Multiple performance enhancements break through application limitations

Developing "multifunctional composite color-coated coils": For example, "antibacterial"

"+ Insulation + Self-Cleaning" three-in-one roll (for hospital roofs, continuously formed to meet multiple needs); "Photovoltaic Power Generation + Decoration" color-coated roll (coated with a transparent conductive coating, continuously processed into photovoltaic curtain wall panels to generate electricity); "Fireproof + Weather-Resistant" color-coated roll (oxygen index ≥ 32%, B1 fireproof, suitable for high-rise buildings).

Customization: Adapt to specific production line requirements

Provide "full-dimensional customization": Customize roll width according to production line width (e.g., 1800mm wide roll for large building molding machines), customize roll weight according to product weight (e.g., 10-ton lightweight roll for small appliance stamping lines), customize coating by function (e.g., high-wear-resistant roll for container production lines); combine 3D Simulation technology enables pre-optimization of coil tension parameters (to prevent deviation during continuous processing).

Intelligent: Full Lifecycle Traceability and Control

A unique QR code (including substrate material, coating type, production batch, and weathering life) is printed on the surface of the color-coated coil. Downstream companies can scan the code to obtain processing parameters (such as stamping pressure and forming temperature). A cloud-based database is established to monitor the coil storage environment (temperature and humidity) and processing loss rate in real time, achieving intelligent control of the entire "production-storage-processing" process.

Conclusion

Color-coated coil, combining "color coating functionality" with "coil efficiency," addresses the pain points of ordinary steel coils (low offline painting efficiency and uneven coating) while also addressing the difficulty of color-coated sheet metal adapting to continuous production lines. It has become an "efficiency engine" for large-scale industrial manufacturing. From continuous forming of color-coated steel sheets in factories to batch stamping of home appliance casings, from automated welding of containers to rapid prefabrication of modular houses, color-coated coils are used throughout the "construction-home appliance-transportation" industry. In the future, with breakthroughs in environmentally friendly coatings, functional integration, and intelligent technologies, color-coated coils will further enhance the efficiency and added value of large-scale production, becoming the "core basic coil material" supporting the upgrading of high-end manufacturing.