Colour-coated hydrophilic aluminium panels are functional panels developed based on traditional colour-coated aluminium panels, featuring **hydrophilic properties** achieved through special surface treatment. They retain the colour diversity and decorative appeal of colour-coated aluminium panels while offering core advantages such as efficient water repellency, anti-condensation, and ease of cleaning. These panels are widely used in evaporators and condensers of refrigeration equipment such as air conditioners, refrigerators, and air-source heat pumps, as well as in building decoration applications in humid environments. The following analysis covers technical principles, core characteristics, and application scenarios:
1. Core Technology of Colour-Coated Hydrophilic Aluminium Panels: From Coating to Hydrophilic Functionality
The ‘hydrophilic properties’ of colour-coated hydrophilic aluminium panels are not naturally inherent but are achieved through a base material pre-treatment + functional coating composite process. The core technical pathways include:
1.Base Material Selection: Aluminium Substrates Suitable for Functional Requirements
- Typically, 1-series (pure aluminium) or 3-series (aluminium-manganese alloy) aluminium sheets with a thickness of 0.1–0.3 mm (commonly used for air conditioning heat exchanger fins) are selected, which offer excellent ductility and thermal conductivity:
- 1-series pure aluminium: Purity ≥99.5%, high thermal conductivity (237 W/(m·K)), suitable for high heat exchange efficiency requirements;
- 3-series aluminium-manganese alloy: Manganese is added to enhance strength, offering superior corrosion resistance compared to pure aluminium, making it suitable for humid environments.
- The substrate surface must undergo **degreasing, phosphating, or chromate treatment** to remove oil residues and oxide layers, enhance coating adhesion, and prevent peeling in later stages.
2. Hydrophilic coating technology: the carrier of core functions
Hydrophilic coatings are the ‘soul’ of colour-coated hydrophilic aluminium sheets. They achieve optimised surface ‘wettability’ by adding hydrophilic groups (such as hydroxyl or carboxyl groups) or nano-scale hydrophilic materials** to the colour-coated primer or topcoat. Mainstream coating types include:
(1) Organic hydrophilic coating (mainstream application)
- Composition: Based on polyester or acrylic resin, with hydrophilic additives (such as polyethylene glycol, surfactants) and nano-silica (to enhance wear resistance);
- Process: Applied via roller coating or spraying onto the surface of colour-coated aluminium sheets, with a thickness of 3–5 μm (thinner than traditional colour coatings to avoid affecting thermal conductivity);
- Hydrophilic principle: Hydrophilic groups in the coating form hydrogen bonds with water molecules, reducing surface tension and causing condensation to spread into a film rather than form droplets.
(2) Inorganic hydrophilic coating (high-end applications)
- Composition: Primarily composed of inorganic materials such as silica sol and titania sol, formed into a porous structure via the sol-gel method, utilising capillary effects to adsorb water molecules;
- Advantages: High temperature resistance (can withstand temperatures above 150°C), excellent ageing resistance, suitable for long-term high-temperature and high-humidity environments (such as heat pump condensers);
- Limitations: Weak colour expression, mostly transparent or light-coloured, lower decorative properties than organic coatings.
(3) Composite coatings (functional layering)
- Utilises a three-layer structure of ‘primer (corrosion protection) + coloured topcoat (decorative) + hydrophilic topcoat (functional)’, balancing colour diversity, corrosion resistance, and hydrophilicity:
- Primer: Epoxy resin or polyurethane, providing adhesion and corrosion resistance;
- Topcoat: Polyester or fluorocarbon coating, providing colour and basic weather resistance;
- Topcoat: Hydrophilic functional layer, 1–2 μm thick, ensuring hydrophilic performance without affecting thermal conductivity.
3. Performance Optimisation Process: Ensuring Functional Stability
- Curing process: High-temperature baking at 180-220°C to cross-link and cure the coating, ensuring stable adhesion of hydrophilic groups and preventing degradation of hydrophilic performance over time;
- Surface microstructure control: Using nanoimprint technology to create micron-level uneven structures on the coating surface, increasing contact area with water and enhancing wettability;
- Weather Resistance Enhancement: UV absorbers and antioxidants are added to prevent coating degradation caused by sunlight or high temperatures, with hydrophilic performance efficacy lasting up to 8–10 years (air conditioning industry standard).
II. Core Characteristics of Colour-Coated Hydrophilic Aluminium Panels: Dual Advantages of Functionality and Aesthetics
1. Hydrophilic Core Functionality: Enhancing Equipment Efficiency and Stability
- Efficient hydrophobic anti-condensation:
Condensate rapidly spreads into a uniform water film on the surface (contact angle ≤30°), rather than condensing into droplets that fall off, preventing droplets from blocking the gaps between heat exchanger fins and ensuring a 15%-20% increase in airflow;
- Enhanced Heat Exchange Efficiency:
The larger contact area between the water film and air facilitates more thorough heat transfer, improving air conditioning cooling efficiency by 5%-8% and achieving significant energy savings;
- Mould-resistant and corrosion-resistant:
The rapid flow of the water film reduces moisture retention, lowering the risk of mould growth (mould survival rate decreases by over 60%), while the coating isolates water vapour from aluminium contact, achieving salt spray resistance of over 500 hours.
2. Decorative colour coating: Expanding application scenarios
- Colour diversity: Through colour-coated topcoats, pure colours (white, grey, blue, etc.) and matte/high-gloss effects can be achieved, meeting aesthetic requirements for equipment appearance or architectural decoration;
- Surface texture options: In addition to traditional flat surfaces, embossing and brushing processes can be combined to add textural decoration while maintaining hydrophilicity, suitable for indoor humid environments (such as bathroom walls);
- Customised adaptation: Adjust the coating gloss (30°-80°), colour saturation, and even print simple patterns according to requirements, balancing functionality and design aesthetics.
3. Physical properties: Suitable for harsh environments
- Temperature resistance: Long-term operating temperature range of -40°C to 120°C (special coatings can reach 150°C), adapting to temperature fluctuations caused by air conditioning cycles;
- Mechanical strength: Coating adhesion reaches Grade 0 (no peeling in cross-hatch adhesion test), scratch resistance ≥3H (pencil hardness), and withstands friction during equipment assembly;
- Lightweight: Density is only 2.7 g/cm³, 60% lighter than copper, reducing equipment weight, suitable for mobile air conditioners, vehicle-mounted refrigeration equipment, and other applications.
III. Typical application scenarios: from industrial equipment to building decoration
1. Refrigeration and HVAC equipment (core application areas)
- Air conditioner evaporators/condensers: heat exchange plates for household air conditioners and central air conditioners; hydrophilic coatings reduce condensation residue, improve heat exchange efficiency, and reduce air resistance and noise;
- Refrigerator evaporators: Prevents uneven frosting that reduces cooling efficiency; hydrophilic properties accelerate defrosting water drainage, reducing the risk of cabinet corrosion;
- Air-source heat pumps: In low-temperature, high-humidity environments, hydrophilic coatings prevent evaporator frosting and blockages, ensuring stable heating performance.
2. Building decoration in humid environments
- Bathroom walls/ceilings: Hydrophilic coatings allow water vapour to diffuse quickly, reducing condensation droplets, while resisting moisture corrosion and preventing rust and discolouration of traditional aluminium panels;
- Kitchen countertop splashbacks: Resistant to grease and easy to clean, water droplets and grease can be quickly wiped away to maintain a clean surface;
- Underground garage ceilings: In high-humidity environments, hydrophilic properties prevent condensation and water accumulation, while decorative colour coatings enhance the aesthetic appeal of the space.
3. Special industrial applications
- Dehumidifiers/humidifiers: Core heat exchange components use colour-coated hydrophilic aluminium panels to improve moisture handling efficiency, while colour coatings facilitate identification of internal equipment structures;
- Cold chain logistics equipment: The hydrophilic coating on the interior walls of refrigerated vehicles and the side panels of refrigerators reduces condensation adhesion, while antimicrobial additives (such as silver ions) inhibit bacterial growth;
- Marine environment equipment: In high salt fog environments, the corrosion-resistant hydrophilic coating protects aluminium from corrosion, making it suitable for marine air conditioning and offshore platform refrigeration equipment.
4. Core differences from ordinary colour-coated aluminium sheets and hydrophilic aluminium foil
Comparison dimension Colour-coated hydrophilic aluminium sheet Ordinary colour-coated aluminium sheet
Core Functionality Hydrophilic anti-condensation + colour decoration Colour decoration + basic corrosion resistance
Coating Structure Primer + colour-coated topcoat + hydrophilic topcoat Primer + colour-coated topcoat
Hydrophilic Performance Contact angle ≤30°, long-term stability Contact angle >90° (hydrophobic)
Decorative Properties Diverse colours, customisable textures Diverse colours, but no hydrophilic properties
Application Scenarios Decorative applications in humid environments + moderate to low thermal conductivity requirements Decorative applications in dry environments-
Summary
Colour-coated hydrophilic aluminium panels, through their composite design combining ‘decorative colour coating + hydrophilic functionality,’ break through the limitations of traditional aluminium panels' ‘single functionality,’ simultaneously meeting aesthetic requirements for equipment or spaces while addressing issues such as condensation, corrosion, and efficiency degradation in humid environments. From the efficient operation of air conditioning heat exchangers to the dry and clean walls of bathrooms, colour-coated hydrophilic aluminium sheets are leveraging their ‘multi-functional’ advantages to become an important functional material in industrial equipment and architectural decoration, driving the deep integration of ‘practicality and aesthetics.’
