Addressing material selection and interaction to optimise performance in water-based metal coatings.
When it comes to protecting metal surfaces, the traditional two-coat system, consisting of a primer followed by a finishing coat, is the most used method. Although effective, this system can be both labour and time-intensive, resulting in higher costs. A more efficient alternative is direct-to-metal (DTM) coatings, which combine the protective qualities of a primer with the aesthetic finish of a topcoat in one application. By using DTM coatings, manufacturers or applicators can reduce costs, paint labour cost, and time without compromising on quality.
The benefits of DTM coatings extend beyond efficiency. Being single-layer, DTM coatings use less material compared to traditional multi-coat systems, helping to save resources. Additionally, by reducing the number of coats and formulating water-based (WB), fewer volatile organic compounds (VOCs) are emitted.
The development of WB DTM coatings necessitates a precise balance of resin chemistry, pigment selection, additive compatibility, and application techniques. The formulation must optimise film thickness, barrier properties, adhesion, and corrosion resistance while maintaining compliance with low-VOC regulations. Proper optimisation of raw materials and interactions—particularly the choice of dispersants, anticorrosive pigments, and fillers—plays a crucial role in achieving high-performance corrosion resistant coatings.
Benefits:
The water-based DTM formulations we developed, overcome several technical hurdles:
- Solid content and film thickness: WB coatings typically have lower solid content, resulting in a thinner protective layer and reduced barrier properties.
- Water sensitivity: The presence of emulsifier in the formulation increases the risk of water absorption, potentially leading to reduced durability and increased corrosion susceptibility.
- Gloss and weather resistance: Achieving high gloss in WB coatings is more difficult compared to solvent-based (SB) formulations, and exposure to outdoor conditions can further degrade the coating.
- Adhesion without primer: Water-based DTM coatings must adhere effectively to various substrates without a separate primer, requiring optimised resin and additive selection.
- Corrosion protection: The right balance of anticorrosive pigments, fillers, and dispersing additives is essential to maximise resistance against rust and environmental degradation.
Key materials:
The composition of WB DTM coatings plays a crucial role in their effectiveness. The primary components include:
- Water-based dispersion resin: Impacts adhesion, mechanical properties, gloss, weather resistance, and corrosion protection.
- Anticorrosive pigments and functional fillers: The interaction between functional fillers and anticorrosive pigments, such as wollastonite, leucophyllite, and talc with zinc aluminium phosphate and zinc phosphate, plays a key role in performance.
- Additives: Selecting the right wetting/dispersing agents, defoamers, surface modifiers, adhesion promoters, rheology additives, and pH neutralisers helps application and appearance without affecting durability.
Formulation support:
Developed in our laboratories, our formulations use best-performing raw material combinations to meet market and customer requirements, ensuring optimal performance for different applications and conditions.
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