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A painted aluminum sheets 4x8 measures 4 feet by 8 feet (1 foot = 304.8 mm), which translates to 1219.2 mm by 2438.4 mm (often simplified to 1220 mm by 2440 mm in actual production for easier procurement and processing). This is a common standard size for color coated aluminum sheet, commonly used in architecture, decoration, and billboard production.

"4x8" is a simplified representation of the Imperial system, corresponding to 1220 mm (width) by 2440 mm (length) in the metric system. This is the "standard large sheet size" for painted aluminum sheet.

Width (4 feet): 1220 mm is the "golden width" for sheet processing—it accommodates most building wall/ceiling modules (such as tile and stud spacing) while also reducing cutting waste.

Length (8 feet): 2440 mm balances transportation convenience (standard trucks can load horizontally) with construction efficiency (a single sheet covers a large area, minimizing joints).

Painted aluminum sheet isn't made of a single material, but rather a composite structure of "aluminum alloy substrate + multi-layer coating." Its performance is determined by both the substrate and the coating, which is also a key consideration when choosing the "4x8" format.

1. Base Material: Aluminum Alloy Sheet

The base materials for "4x8" color painted aluminum sheet are typically 1xxx series (pure aluminum), 3xxx series (aluminum-manganese alloy), or 5xxx series (aluminum-magnesium alloy). The differences between these series directly impact the sheet's strength, weather resistance, and applicable applications. A specific comparison is as follows:

- 1xxx series (e.g., 1060, 1100):

Pure aluminum (Al ≥ 99.6%): Good plasticity and easy cutting and bending, but relatively low strength. Suitable for interior decoration (e.g., backdrops, display racks) and lightweight billboards.

- 3xxx series (e.g., 3003, 3004, 3104, 3105):

Aluminum + manganese (Mn ≈ 1.5%): 30% stronger than 1-series and excellent corrosion resistance. Suitable for lightweight outdoor structures (e.g., awnings, temporary enclosures) and indoor suspended ceilings.

- 5xxx series (e.g., 5052):

Aluminum + magnesium (Mg ≈ 2.5%): High strength, high weather resistance, and wind and impact resistance. Suitable for high-demand outdoor applications (such as building exteriors, large outdoor billboards, and vehicle body panels).

2. Coating: Multi-layer protective structure (determines appearance and weather resistance).

The coating is the "protective layer + decorative layer" of pre-painted aluminum sheets. The industry's mainstream structure is a four-layer structure of pretreatment layer + primer + topcoat + backcoat. Some high-end products add a "clearcoat" layer to improve scratch resistance. The functions of each layer are as follows:

- Pretreatment layer

Strengthens adhesion between the substrate and the primer and prevents oxidation. Processes include chromizing (traditional) and chromium-free passivation (environmentally friendly). Adhesion ≥ 5MPa (cross-hatch test).

- Primer

Further enhances adhesion and blocks moisture and oxygen from reaching the substrate. Common materials include epoxy primer and polyester primer. Salt spray resistance ≥ 500 hours (rust-free).

- Topcoat

Determines appearance (color/gloss) and provides primary weather resistance. Common materials include polyester paint (indoor use), fluorocarbon paint (outdoor use), and silicone-modified polyester paint (mid- to high-end). Polyester paint: Weather resistance 1-3 years (indoor);

Fluorocarbon paint: Weather resistance 10-20 years (outdoor UV protection).

- Backcoat

This protects the back of the board from scratches during transportation and installation. Common materials include epoxy backcoat and simple polyester paint. There are no specific appearance requirements; the main focus is on adhesion.

Key Parameters of 4x8 Painted Aluminum Sheets

In addition to size, the following parameters directly impact performance and cost, so please specify them clearly when purchasing:

- Thickness:

This includes "substrate thickness" and "coating thickness," which must be expressed separately.

Substrate thickness: Commonly 0.3mm-1.5mm (thinner than 0.3mm is prone to deformation, and thicker than 1.5mm is difficult to process). For example, "0.5mm substrate + 0.02mm coating" yields a total thickness of approximately 0.52mm.

Coating thickness: Topcoat thickness is typically 15-25μm (fluorocarbon paint can be thicker, reaching 25-35μm). The more uniform the thickness, the more stable the weather resistance.

- Colors:

Commonly available in white, black, gray, blue, and red (custom color charts, such as Pantone, are available);

- Gloss:

Matte (below 30°), semi-matte (30°-60°), and glossy (above 60°). Matte is recommended for outdoor use to reduce light pollution and thermal expansion and contraction.

- Weather Resistance:

For outdoor use, pay attention to UV resistance (Xenon lamp aging test ≥ 1000 hours, color difference ΔE < 3) and salt spray resistance (≥ 1000 hours for coastal areas).

- Processing Performance:

Bending radius (e.g., for 0.5mm thick 3xxx series painted aluminum sheet, the minimum bending radius is approximately 5mm to avoid coating cracking during bending) and cut edge flatness (no burrs).

- Weight Calculation:

Aluminum sheet density is approximately 2.7g/cm³. Taking a sheet measuring 1220mm x 2440mm x 0.5mm as an example, a single sheet weighs approximately 122 x 244mm x 0.05 x 2.7, which is approximately 40.6kg (for ease of transport weight estimation).

- Coverage:

Net area per sheet is approximately 1220mm x 2440mm, which is approximately 2.98㎡ (the actual construction area should be deducted from the joint seams, resulting in an approximate area of 2.8-2.9㎡ per sheet).

Applications and Advantages of Painted Aluminum Sheets 4x8:

Due to its size and performance characteristics, this specification of painted aluminum sheets has highly focused applications and offers significant advantages over other materials (such as color-coated steel sheets and solid wood panels):

- Architectural Decoration:

Indoor ceilings (3xxx series thin base material, lightweight), exterior wall hangings (5xxx series thick base material + fluorocarbon paint, wind-resistant), and balcony railing panels;

- Advertising Signage:

Large outdoor billboards (4x8 size reduces splicing, fluorocarbon paint offers sun resistance), light box panels (thin base material + translucent coating);

- Industrial Support:

Equipment casings (corrosion-resistant), interior/exterior vehicle walls (5xxx series high-strength, impact-resistant), and cleanroom walls (easy to clean, no dust shedding).