⚠️ The core of the aluminum composite panel is PE materials. It must never be baked at high temperatures. Only two-component, room-temperature, air-drying paint can be used. Baking will cause the PE to soften, the aluminum composite panel to bubble and delaminate.

The original panel surface has a polyester/fluorocarbon coating. Direct spraying will easily cause the entire panel to peel off. The primer is crucial for success.

I. Mandatory Technical Requirements for Paint

1.Curing Conditions

◎Two-component, room-temperature air-drying (5-35℃ natural curing).

◎Baking above 100℃ is prohibited.

◎The temperature limit for the PE core is approximately under 80℃; exceeding this temperature will cause the panel to deform and blister.

2. Primer Requirements (Mandatory, Cannot be Omitted)

Preferred to adopt Epoxy Zinc Yellow Primer or Epoxy Zinc Phosphate Aluminum-Specific Primer. It’s suitable for painted polyester and fluorocarbon panels. Adhesion will up to grade 1and dry film thickness be up to 20-30μm.

❌ Ordinary epoxy zinc-rich primer is prohibited. Zinc powder systems have poor adhesion to aluminum surfaces and are prone to peeling.

3. General Topcoat Specifications

◎Adhesion: Cross-cut test will up to grade 1; Pencil hardness ≥H;

◎Salt spray resistance: Outdoor ≥1000h; Artificial aging 500-3000h depending on grade;

◎Total dry film thickness (primer + topcoat): Indoor 35-50μm; Outdoor 50-70μm; Apply in 2-3 thin layer coats will avoid thick coats in one application to prevent cracking and sagging.

4.Compatibility Principle

◎The primer and topcoat resin systems must be compatible.

◎The paint manufacturer must conduct compatibility tests

◎A small sample must be prepared before mass production: after spraying for 72 hours, perform a cross-cut adhesion test to confirm no paint peeling before proceeding with mass production.

II. Topcoat Recommendations (by Application Scenarios)

Solution A: Outdoor Exterior Walls, Curtain Walls (High Weather Resistance, Prioritized for Export Projects)

◎System: Epoxy Zinc Yellow Primer + Room Temperature Curing Two-Component Fluorocarbon Topcoat (PVDF)

◎Weather resistance: 15 years warranty of excellent color stability and gloss retention, UV-resistance and acid-resistance; suitable for metallic and pearl colors.

◎Standard reference: Compliant with HG/T3792-2014 Type III Fluorocarbon Paint for Metals

◎Disadvantages: High cost; long-time for color matching.

Solution B: Outdoor Billboards, Facades, Engineering Projects (Most Cost-Effective and Commonly Used)

◎System: Epoxy Zinc Yellow Primer + Two-Component Aliphatic Polyurethane (PU) Topcoat

◎Weather resistance: 5-8 years; adjustable gloss unit, stable for both solid and metallic colors; moderate overall cost, most commonly chosen for export projects.

⚠️Do not use aromatic polyurethane, as it is prone to yellowing when used outdoors.

Option C: Interior Projects (Interior Walls, Ceilings)

◎System: Epoxy Zinc Yellow Primer + Two-Component Acrylic Polyurethane Topcoat

◎Lifespan: 3-5 years; Low cost, a wide range of colors and finishes; Not recommended for outdoor use, as it is prone to fading and loss of gloss.

❌Not Recommended: Single-component spray paint, ordinary alkyd paint; poor adhesion and will peel off quickly. Powder coating is completely unusable (requires high-temperature baking, aluminum composite panels will be rendered unusable).

III. Surface Treatment Requirements Before Spraying (Very critical; even the best paint will peel if not properly treated)

1. Sanding

◎Lightly roughen the surface evenly with 240-400 grit sandpaper/scouring pad.

◎Do not sand through the original aluminum layer. It must achieve a uniform matte finish and avoid localized sanding omissions.

2. Degreasing: Wipe the entire surface with isopropyl alcohol/anhydrous alcohol to remove release agent, oil, and dust, then blow away dust with compressed air.

3. Drying

◎The panel surface must be completely dry before painting.

◎The application humidity should be ≤70%, and the temperature 10-30℃. Avoid rainy days.

4. Edge and Corner Protection: The cut edges of the aluminum composite panel should be sealed with a thin layer of paint to prevent moisture from seeping into the core material and causing blistering of the paint film.

IV. Risk Warnings (To be communicated to customers in advance)

1. This is a repainting color of finished aluminum composite panels. If not original factory roller coating of aluminum coils, performance will be slightly lower than original factory roller-coated fluorocarbon panels. And outdoor use has an aging period, and the expected lifespan must be explained to the customer.

2. Color samples must be confirmed and signed for confirmation before bulk orders. And color differences may occur between different batches of paint and spray thickness.

3. The paint film requires 7 days to fully cure. Do not fold, bend, or apply heavy pressure within 7 days of spraying. Bending may cause the paint surface to crack, so avoid bending after spraying.

4. Export Goods: A corresponding MSDS is required for the paint; Some countries require a VOC test report.

V. Simplified Work Process Chart

Degreasing of the board → Light sanding and roughening → Dust removal and degreasing → Spraying epoxy zinc yellow primer (dry to 20-30μm) → Fully dry for primer (12-24h) → Light dust removal → Spraying topcoat in 2 coats → Natural curing at room temperature for 7 days before packaging and shipping.