In the coatings industry, product quality is always tied to system stability. Yet many paint batches develop sedimentation during storage or even after application. This defect reduces re-dispersibility, making the surface uneven and prone to early degradation. Sediment not only affects the appearance but also compromises durability and protective function. Many manufacturers face heavy losses when paint suffers this fault. To overcome it effectively, the root causes must be identified and proper solutions applied.
CAUSES OF SEDIMENTATION IN WATER-BASED PAINT
Dispersion instability and pH change
One of the most common reasons for sedimentation is poor dispersion stability. When dispersants are insufficient, pigment and filler particles aggregate into clusters. The paint settles quickly and is difficult to re-disperse. pH shifts also strongly affect emulsion stability. Most polymers stay stable only within a narrow pH range. When pH drops too low, the emulsion structure collapses, leading to gelation. The paint becomes viscous and cannot be applied evenly.
Metal ion interactions and additive incompatibility
Production water that is not properly treated often contains metal ions such as Ca²⁺, Mg²⁺, or Fe³⁺. These ions react with dispersants, causing flocculation and paint clumping. Certain pigments, especially untreated TiO₂, further increase this risk. Besides ions, unwanted reactions between additives can also trigger sedimentation. A common case is silicone defoamers conflicting with polymeric dispersants, or resins incompatible with thickeners. The system loses stability, resulting in phase separation and gel residues.
Temperature, storage time, and microbial growth
High storage temperatures accelerate side reactions among paint components. Above 40°C, emulsions easily lose stability. Conversely, freezing and thawing also damage the original structure. Extended storage makes the problem more severe, leading to sedimentation or phase separation. Moreover, waterborne paint is highly vulnerable to microbes. Bacteria and fungi can thrive, forming sticky gels or surface films. They not only cause sediment but also produce unpleasant odors and reduce protective performance.
SOLUTIONS TO PREVENT AND CONTROL SEDIMENTATION
pH control and effective dispersants
To maintain emulsion stability, the paint pH should be kept between 8.0 and 9.0. This can be achieved by adding ammonia or amines during production. pH monitoring is vital not only in processing but also during storage. Choosing high-performance dispersants is equally crucial. Modern dispersants offer multi-dimensional stabilization, combining electrostatic repulsion and steric hindrance to prevent aggregation. For systems containing TiO₂ or carbonate fillers, specialized dispersants are highly recommended.
Water treatment and additive compatibility
Process water must be thoroughly purified to remove heavy metal ions. RO filtration or ion-exchange technologies are preferred solutions, eliminating flocculation risks at the source. In addition, every additive must be tested for compatibility before formulation. Resins, thickeners, dispersants, hydrophobics, and biocides should all be checked in advance. This precaution helps prevent unexpected reactions that lead to sedimentation.
Biocide protection and storage management
To prevent microbial growth, suitable preservatives must be added to the paint. Biocides such as CMIT/MIT or BIT are recommended at 0.1–0.2% concentration. They effectively suppress bacteria and fungi, ensuring long-term stability. Proper storage conditions are also essential. Paint should be kept in ventilated warehouses, below 30°C, and away from direct sunlight. Freezing or overheating must be avoided, as both conditions deteriorate quality and accelerate sediment formation.
VICHEM – AUTHORIZED DISTRIBUTOR OF COATING ADDITIVES IN VIETNAM
Vichem is an official distributor of coating additives with full regulatory compliance in Vietnam. We provide not only quality products but also international-standard after-sales services. Our services include:
- Technical consulting: helping customers select the most suitable products for their applications.
- Color matching tests: our experts perform evaluation to ensure design-standard results.
- Application support: assisting customers in integrating solutions into their production lines for optimal efficiency.
For more information, please contact us through the following channels:
📞 Hotline: 08 1790 1790
📧 Email: contact@vichem.vn
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🌐 Website: www.vichem.vn
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