Paint color change is a common phenomenon after a period of use, especially on outdoor surfaces. Many people believe the main cause is sunlight and ultraviolet radiation, but in reality, there are many other factors that affect tone and gloss. From oxidation reactions to humidity and resin quality, every element contributes to color transformation over time. Understanding this mechanism helps select suitable products, apply the right techniques, and maintain long-lasting color stability.
PAINT COLOR CHANGE PHENOMENON
Paint color change is the process in which the coating becomes discolored, loses gloss, or turns yellowish after a period of use. It reflects material aging when the resin and pigment are altered by environmental impacts. There are two main types: fading and yellowing. Fading reduces pigment intensity, while yellowing gradually shifts the paint to warmer tones. Both reduce aesthetics and surface protection. The degree of color change depends on light, temperature, humidity, and application quality. In harsh environments, especially outdoor projects, the fading process occurs many times faster than indoors.
EFFECT OF UV RAYS ON PAINT COLOR
Ultraviolet rays (UV-A, UV-B) are the most common cause of color fading. When light hits the surface, photon energy breaks polymer bonds in the resin, reducing transparency and degrading organic pigments. The result is a faded, dull, and shallow coating. In tropical regions, particularly on west- or south-facing walls, this effect becomes more pronounced. However, UV rays are only part of the chain of causes. Color durability also depends on chemical reactions, humidity, resin quality, and pigment stability.
OTHER CAUSES OF PAINT COLOR CHANGE
Oxidation reaction and resin degradation
When exposed to oxygen and heat, alkyd, epoxy, or acrylic resins all oxidize. Polymer chains break, causing the resin to turn yellow or brown and altering the overall color. Oxidation also makes the coating brittle, prone to cracking, and less adhesive. Even when improperly stored, this process can occur before application.
Instability of pigments
Pigments determine color strength and brightness, but not all types are stable. Organic pigments such as azo or phthalocyanine degrade quickly under strong light and solvents. In contrast, inorganic pigments like iron oxide, titanium dioxide, and chromium green are highly durable and ideal for exterior paints. Choosing the wrong pigment or an incompatible resin system can cause color change within months.
Ảnh hưởng của ô nhiễm và hóa chất môi trường
Urban air contains gases such as SO₂, NOx, fine dust, and industrial solvent vapors. These substances react with the paint surface, forming salts or gray films that distort color. In industrial zones or dense traffic areas, exterior paints fade twice as fast as those in cleaner environments. Additionally, slightly acidic rainwater contributes to surface corrosion and reduces color brightness.
SOLUTIONS TO LIMIT PAINT COLOR CHANGE
Selecting durable materials and technologies
Raw materials are the key to preventing color fading. It is recommended to use inorganic pigments with high lightfastness combined with UV-resistant resins and light stabilizer additives. High-performance resin systems such as fluorocarbon, polyurethane, or premium acrylics feature stable structures, excellent weather resistance, and low oxidation. Advanced dispersion technologies also help create a uniform coating, minimizing light refraction and maintaining consistent tones.
Controlling environmental conditions during use
Do not apply paint when humidity is high or temperatures exceed recommended limits. Excessive heat causes rapid solvent evaporation, preventing proper film formation. Conversely, humid air condenses moisture, leading to bubbles and white spots. During storage, paint should be kept in a dry, well-ventilated area away from direct sunlight. Always seal containers tightly after use to prevent solvent evaporation and early oxidation.
Proper application and maintenance
The application process directly affects color durability. The surface must be clean, dry, and free from oil or dust. The paint should be applied at the correct thickness with appropriate drying time between coats. If the previous layer is not completely dry, remaining solvent may alter the tone of the upper layer. After application, the surface should be cleaned periodically with water to remove dust and chemical residues. Avoid using strong detergents or metal brushes, as they can damage the coating.
VICHEM – OFFICIAL DISTRIBUTOR OF CHEMICAL ADDITIVES FROM COVESTRO, SINOPEC, AND TINOX IN VIETNAM
Vichem is the authorized distributor of chemical additives from major global brands such as Covestro, Sinopec, Tinox, and TotalEnergies in Vietnam, fully compliant with local legal regulations. We not only provide high-quality products but also deliver international-standard after-sales services. Our services include:
- Technical consulting: Helping customers select the right product for their specific application.
- Color testing: Vichem’s expert team conducts color-matching trials to ensure the final result meets design standards.
- Application support: Assisting clients in integrating products into production lines for optimal performance.
For more information, please contact us through the following channels:
📞 Hotline: 08 1790 1790
📧 Email: contact@vichem.vn
🔎 LinkedIn: Vichem JSC
🌐 Website: www.vichem.vn
📌 Facebook: Vichem JSC
