1. Introduction

Water-based color pastes have become essential colorants for eco-friendly industrial coatings as global environmental regulations tighten VOC emissions. Dongguan DENSON Functional Materials Co., Ltd. (DENSON) has developed the GT series of pure water-based color pastes, designed with water as the sole dispersion medium and VOC content below 50 g/L, fully compliant with GB 30981-2020 and GB/T 38597-2025 low-VOC requirements. This article examines the dispersion mechanism, application performance, and selection parameters of GT series water-based color pastes in industrial coating systems, including waterborne epoxy, polyurethane, and amino baking finishes.

The transition from solvent-borne to water-borne coatings in industrial applications—structural steel, construction machinery, automotive components—requires color pastes that maintain pigment stability in high-ionic-strength aqueous systems. The GT series addresses this challenge through a dual stabilization mechanism combining electrostatic repulsion and steric hindrance.

For more DENSON color paste technical resources, visit the application literature section.

2. Technical Features and Dispersion Mechanism

Pure water-based color paste is a high-concentration pigment dispersion using deionized water as the continuous phase, high-performance organic/inorganic pigments as the dispersed phase, and water-based hyperdispersants as the stabilizing system.

2.1 Dual Stabilization Mechanism

In aqueous systems, pigment particles are stabilized through two complementary mechanisms:

Electrostatic stabilization (DLVO theory): Ionic dispersant functional groups (carboxylate -COO⁻, sulfonate -SO₃⁻, phosphate -PO₄³⁻) adsorb onto pigment surfaces, creating an electrical double layer. The high dielectric constant of water (ε=78.5 at 25°C) extends the Debye length to approximately 9.6 nm at 10⁻³ mol/L electrolyte concentration, providing a broader electrostatic repulsion range compared to solvent systems.

Steric stabilization: Nonionic hydrophilic polymer chains (PEG, PAA, PVP) extend into the aqueous phase, forming an adsorbed layer of 5-20 nm thickness. When particles approach, osmotic repulsion and volume restriction effects prevent aggregation.

2.2 Key Technical Specifications

2.3 Academic Research Context

Recent research in Journal of Applied Polymer Science (2025, DOI: 10.1002/app.56144) demonstrated that PEGylated partially hydrolyzed poly(N-vinyl amide) block copolymers achieve carbon black dispersions with mean particle size 85 nm and zeta potential -42 mV at 20 wt% loading, with less than 8% particle growth after 30 days at 50°C. ACS Applied Polymer Materials (2026, 8(6), 4573-4586, DOI: 10.1021/acsapm.6c00349) reported soft-core/hard-shell gradient copolymer pigment encapsulation via RAFT polymerization, reducing particle size distribution span from 0.82 to 0.41 for phthalocyanine blue aqueous dispersions.

Figure 1. Water-based coating production facility (feeding station and finished goods warehouse)

3. Application Case 1: Waterborne Epoxy Anti-Corrosion Coatings for Structural Steel

Project background: A major structural steel manufacturer (150,000 tons annual capacity) transitioned from solvent-borne epoxy zinc-rich primer + polyurethane topcoat to a fully waterborne system to meet GB 30981-2020 VOC requirements.

Coating system:

Application method: Airless spraying at 32:1 pressure ratio, 0.031-0.035 inch tip. Surface preparation: blast cleaning to Sa 2.5, roughness Rz 40-75 μm. Application conditions: 10-35°C, RH ≤85%, steel surface temperature at least 3°C above dew point.

Performance results:

4. Application Case 2: Waterborne Polyurethane Topcoats for Construction Machinery

Customer: A construction machinery manufacturer producing excavators and wheel loaders (800 tons annual coating consumption), requiring excellent weatherability and batch color consistency (ΔE ≤0.5).

Binder system: Waterborne hydroxy acrylic dispersion + waterborne HDI curing agent, two-component, NCO/OH molar ratio 1.1-1.2.

Color formulations:

Application: Rotary bell electrostatic spraying, 60-80 kV, 30,000-40,000 rpm, viscosity 25-30 s (Ford #4, adjusted with deionized water). Baking: 80°C flash-off 5 min + 140°C bake 20 min.

Figure 2. Industrial component waterborne coating application (electrostatic spraying in controlled environment)

5. Application Case 3: Waterborne Amino Baking Finishes for Automotive Components

Customer: An automotive component supplier providing bumpers and mirror housings to multiple OEMs, requiring color consistency ΔE ≤0.8 and QUV 1000 h ΔE ≤2.0.

Binder system: Waterborne hydroxy acrylic resin + methylated amino resin, curing at 140°C for 25 min.

Pigment selection: Automotive-grade weather-resistant pigments including C.I. Pigment Yellow 150 (PY150), C.I. Pigment Red 170 (PR170), and C.I. Pigment Blue 15:3 (PB15:3). GT high-weatherability pastes are specifically formulated for these pigments.

Process: Three-coat one-bake system (waterborne primer + waterborne basecoat + clearcoat). Basecoat applied via rotary bell electrostatic spraying, 15-20 μm film thickness. Paste addition controlled at 1%-4% to avoid adverse effects on water resistance and adhesion.

Performance: Adhesion (cross-cut) 0 grade, water resistance (40°C × 240 h) no blistering, gasoline resistance (4 h) no abnormality, QUV 1000 h ΔE = 1.6.

6. Key Selection Parameters and Usage Recommendations

7. Conclusion

DENSON GT series pure water-based color pastes demonstrate excellent dispersion stability and application compatibility in waterborne epoxy anti-corrosion, polyurethane topcoat, and amino baking enamel systems. With VOC content ≤50 g/L, batch color difference ΔE ≤0.3, and salt spray resistance ≥1000 h, these pastes provide a reliable coloring solution for industrial coating waterborne transition, supported by a dual electrostatic-steric stabilization mechanism and system-specific dispersant formulations.

8. FAQ

Q1: How does pure water-based color paste differ from water-oil universal color paste?

A: Pure water-based pastes use water as the sole dispersion medium with VOC ≤50 g/L, designed specifically for waterborne coatings. Water-oil universal pastes contain co-solvents (propylene glycol, butyl glycol) and can be used in both waterborne and some solvent systems but have higher VOC. For strict low-VOC waterborne coatings, pure water-based pastes are recommended.

Q2: What causes flash rust in waterborne industrial coatings and how can it be prevented?

A: Flash rust occurs when water and oxygen form micro-cells on steel surfaces during waterborne coating application. Prevention measures: add 0.1%-0.3% flash rust inhibitor; maintain RH ≤85%; ensure steel surface is at least 3°C above dew point; use zinc-rich epoxy primer for cathodic protection. GT color pastes do not contain components that promote flash rust.

Q3: What is the pot life of waterborne two-component polyurethane after adding color paste and curing agent?

A: Typically 2-4 hours at 25°C. Color paste should be added to the base component and mixed thoroughly before adding the curing agent. After catalyst addition, the mixture should be used within the pot life. Viscosity will noticeably increase beyond the pot life, affecting sprayability.

Q4: How should water-based color pastes be stored?

A: Store at 5-35°C in sealed containers. Below 5°C, ice crystal formation can disrupt the dispersant adsorption layer, causing irreversible flocculation after thawing. Above 40°C, dispersant desorption and accelerated particle motion reduce storage stability. Avoid direct sunlight and freeze-thaw cycles.

Q5: Can different GT color pastes be mixed together for custom color matching?

A: Yes, GT pastes of the same type can be intermixed. Weigh accurately by mass ratio, mix at low speed (300-500 rpm) for 3-5 minutes, and use within 24 hours to prevent pigment segregation. Always conduct a small-scale compatibility test before large-scale production.

For more product information, visit Dongguan DENSON Functional Materials Co., Ltd.