Top 10 Guidelines for Using Pearl Pigments in Powder Coatings

Pearl pigments, with their unique metallic luster and color-shifting effects, have become a game-changer in the powder coating industry. However, improper use can lead to issues like mottling, color deviation, and poor weather resistance. Here are the top 10 guidelines to help you master the application of pearl pigments.

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1. Material Selection: Choose the Right Type for Your Application

Technical Deep Dive:

Base Material Comparison Table

Type

Temperature Resistance

Application Scenarios

Failure Risks

Standard Mica

180-200°C

Home appliances, indoor furniture

Discoloration in high-temperature baking

Silica-Coated

250-300°C

Automotive parts, outdoor equipment

Peeling due to insufficient temperature

Glass Flake

400°C+

Industrial equipment, high-temperature tools

High cost leading to project abandonment

Industry Recommendations: For automotive applications, opt for Merck’s Iriodin® high-temperature series. For home appliances, BASF’s Paliocrom® golden series is highly recommended.

2. Dispersion Process: Control Fragility for Optimal Results

Process Optimization:

Equipment Selection Matrix

Equipment Type

Speed Range

Application Stage

Breakage Rate Control

Twin-Screw Extruder

300-500 rpm

Pre-mixing stage

≤3% (particle size >15μm)

3D Motion Mixer

10-20 rpm

Final mixing stage

≤0.5%

High-Speed Disperser

Not recommended

/

Breakage rate up to 15%

Practical Tip: Use the "resin encapsulation method"—pre-mix 30% resin with pearl pigments at low speed for 5 minutes, then add the remaining ingredients in batches.

3. Formula Compatibility: Avoid Hidden Chemical Reactions

Risk Mitigation:

Resin Compatibility Chart

Resin Type

Risk Reaction

Solution

Carboxyl Polyester

Acid-base reaction with TiO₂ coating

Switch to hydroxyl resin + pH adjuster

Epoxy Resin

Amine curing agents cause surface passivation

Use amine-free curing systems

UV-Curable Resin

Photoinitiators degrade organic pigments

Choose inert-coated pigments

Testing Method: Mix pigment and resin at a 1:5 ratio and store at 80°C for 48 hours. Check for flocculation or discoloration.

4. Orientation Control: Master Electrostatic Spraying Parameters

Optimal Spraying Parameters:

Equipment Settings

▶ Voltage Gradient: 60kV (base layer) → 75kV (effect layer)  

▶ Spray Gun Distance: 20cm (flat surfaces) → 15cm (complex structures)  

▶ Atomization Pressure: 0.4-0.6 bar (avoid airflow disturbance)  

▶ Film Thickness Gradient: Base layer 50μm → Pearl layer 30μm  

Case Study: An electric vehicle manufacturer experienced a 23% rework rate due to "zebra stripes" caused by 90kV over-spraying.

5. Batch Stability: Moisture Control is Critical

Humidity Management System:

Moisture Control Protocol

Raw Material Storage: 25°C±2°C, humidity ≤30% (equipped with molecular sieve dehumidifiers)  

Mixing Room: Localized dry hood (dew point ≤-40°C)  

Production: Use opened pigments within 4 hours  

Reclaimed Powder: Secondary drying at 80°C for 4 hours  

Testing Standard: Follow ISO 787-2, using Karl Fischer titration to ensure moisture content ≤0.3%.

6. Mixing Precautions: Avoid Metal Powder Pitfalls

Optimized Formulations:

Recommended Combinations

Desired Effect

Recommended Formula

Precautions

High Metallic Effect

Pearl pigments + metal oxide composites

Avoid direct aluminum powder use

Soft Pearl Luster

Pearl pigments + transparent pigments

Limit transparent pigments to ≤5%

Colored Pearl Effect

Pearl pigments + inorganic colorants

Avoid organic dyes

7. Weather Resistance: The Ultimate Test for Outdoor Use

Durability Optimization:

Accelerated Aging Test Data

Test Condition

Organic Dyes

Inorganic Coating

Performance Improvement

QUV 1000 Hours

ΔE > 5.0

ΔE < 1.5

70%

Salt Spray 500 Hours

Significant fading

No change

100%

Recommended Products: For outdoor applications, choose Merck’s Xirallic® series with full inorganic coatings.

8. Coating Thickness: Micron-Level Precision

Film Thickness Management:

Flow Test Data

Thickness Range (μm)

Visual Effect

Defect Risk

<60

Poor coverage, substrate visible

Color deviation

80-120

Optimal pearlescent effect

None

>150

Sagging, edge buildup

Uneven surface

9. Reclaimed Powder Management: Ensure Color Consistency

Reclaimed Powder Guidelines:

Usage Ratios and Effects

Reclaimed Powder Ratio

Color Shift ΔE Value

Economic Evaluation

≤10%

<0.5

Excellent

10-15%

0.5-1.0

Good

>15%

>1.5

Poor

10. Inspection Blind Spots: Multi-Angle Light Verification

Inspection Optimization:

Multi-Angle Spectrophotometer Parameters

Observation Angles: 25° (highlight), 45° (mid-angle), 75° (side light)  

Light Source: D65 standard illuminant  

Color Tolerance: ΔE 1.0 (indoor), ΔE 1.5 (outdoor)  


Conclusion: Build a Digital Quality Control System

Implement an MES (Manufacturing Execution System) to monitor key parameters in real-time:

Pigment dispersion (laser particle size analyzer)

Spraying voltage (digital high-voltage generator logs)

Film thickness uniformity (beta-ray thickness gauge)

Color deviation ΔE (multi-angle spectrophotometer)

By establishing a Process Window through data modeling, you can transform the "artistic expression" of pearl pigments into a "precision engineering" process.