Views: 0 Author: Site Editor Publish Time: 2026-08-15 Origin: Site
In industrial coating applications, the spraying process is where the final product quality is determined. Whether using electrostatic powder coating or liquid coating, precise control of material parameters, equipment settings, and curing conditions is essential for achieving optimal coating performance.
This article covers the complete technical standards for:
Powder coating material requirements
Electrostatic spray equipment parameters
Curing process control
Coating performance inspection
Liquid coating technical standards
DINGPRECISION uses two types of thermosetting powder coatings:
表格
Type | Resin System | Application |
|---|---|---|
Indoor type | Polyester resin | Home appliances, electronics, general industrial |
Outdoor type | Polyurethane resin | Energy storage, charging piles, coastal environments |
Particle Size Requirement: D50 = 30-50 μm (measured by laser particle size analyzer)
Too large (>50 μm): Poor flow, rough surface
Too small (<30 μm): Dust flying, low powder deposition efficiency
表格
Inspection Item | Standard | Test Method |
|---|---|---|
Appearance | Loose powder, no foreign matter, no agglomeration | Visual + 40-mesh sieve |
Particle size distribution | D50 30-50 μm | Laser particle size analyzer |
Gel time | 30-90 seconds at 180°C | Hot plate method |
Density | 1.2-1.8 g/cm³ | Pycnometer method |
Curing time | 10-20 minutes at 200°C | Hot plate method |
Storage period | ≤6 months (≤25°C) | Accelerated aging test |
DINGPRECISION operates 3 automated electrostatic powder coating lines, each equipped with automatic reciprocating spray guns (including manual touch-up stations).
表格
Parameter | Control Range | Measurement Method | Notes |
|---|---|---|---|
Spray distance | 150-250 mm | Ruler measurement | Optimal: 200 mm |
Electrostatic voltage | 60-90 kV | High voltage meter | Flat parts: 70-80 kV |
Powder output | 150-350 g/min | Electronic scale (10s test) | Adjust based on target thickness |
Atomizing air pressure | 0.15-0.25 MPa | Air pressure gauge | Critical for thickness uniformity |
Chain speed | 3-6 m/min | Tachometer | Adjust based on part complexity |
Gun reciprocating frequency | 40-80 cycles/min | Controller | 1 primer + 1 topcoat |
表格
Item | Standard | Notes |
|---|---|---|
Target film thickness | 80-120 μm | Standard parts |
Measurement method | Magnetic/eddy current gauge | Per GB/T 13452.2-2008 |
Sampling points | 5 points per test area | Average value |
Thickness uniformity | ±15 μm (standard) | ±10 μm for high-precision |
表格
Parameter | Control Range | Notes |
|---|---|---|
Oven temperature | 180-200°C | Measure from surface temperature rise |
Dwell time | 10-20 minutes | From surface reaching target temperature |
Temperature uniformity | ±5°C | Use oven temperature tracker |
Common Defects from Improper Curing:
表格
Issue | Cause | Effect |
|---|---|---|
Under-curing | Low temperature or short time | Low hardness, poor adhesion |
Over-curing | High temperature or long time | Yellowing, brittleness, gloss loss |
表格
Test | Method | Standard |
|---|---|---|
Preliminary check | Acetone wipe test | No tackiness, no dissolution |
Final adhesion | Cross-cut test (GB/T 9286) | ≥ Grade 4 (≤5% peeling) |
Pencil hardness | GB/T 6739 | ≥ 2H |
表格
Inspection Item | Standard | Method | Frequency |
|---|---|---|---|
Film thickness | 80-120 μm | GB/T 13452.2 (thickness gauge) | First piece + patrol per shift |
Adhesion | ≥ Grade 4 (≤5% peeling) | GB/T 9286 (cross-cut test) | Per shift / per color change |
Pencil hardness | ≥ 2H | GB/T 6739 | Per shift |
Impact resistance | 50 kg·cm, no cracking | GB/T 1732 | Per shift |
Salt spray test | ≥500h (standard) / ≥1000h (high) | GB/T 10125 / ASTM B117 | Monthly / new material |
Color difference (ΔE) | Same batch ≤1.0 / Cross batch ≤1.5 | Spectrophotometer (D65/10°) | Per batch / shift |
Gloss (60°) | ±5° | Gloss meter | Per batch / shift |
DINGPRECISION uses a spectrophotometer (D65 light source / 10° viewing angle / SCI mode) for precise color measurement.
表格
Item | Standard | Notes |
|---|---|---|
Calibration | Per shift using standard color plate | — |
Same batch ΔE | ≤ 1.0 | Industry standard: ≤ 1.5 |
Cross batch ΔE | ≤ 1.5 | Industry standard: ≤ 2.0 |
Out-of-range action | Check curing temperature curve | Adjust formulation if needed |
DINGPRECISION operates 1 liquid coating line (commissioned in 2025) to meet special customer requirements:
High gloss (60° gloss >90)
Metallic / sparkle effects
Transparent coatings
Tactile / soft-touch coatings
表格
Parameter | Control Range | Notes |
|---|---|---|
Film thickness | 40-80 μm | Depends on coating type and color |
Flash-off / Leveling time | 5-10 minutes | At room temperature |
Curing condition (bake) | 80°C × 30 minutes | For standard baking systems |
Curing condition (air dry) | 24 hours at room temperature | For self-curing systems |
VOC emissions | Must comply with national standards | Environmental compliance |
The coating performance inspection standards for liquid coating are identical to those for powder coating (see Table 3-3 above), including:
Film thickness
Adhesion (cross-cut test)
Pencil hardness
Impact resistance
Salt spray resistance
Color difference (ΔE)
Gloss measurement
表格
Defect | Possible Cause | Solution |
|---|---|---|
Orange peel | Poor flow, incorrect particle size | Adjust powder particle size/D50 |
Pinholes | Moisture in substrate or powder | Ensure proper drying and powder storage |
Poor adhesion | Under-curing or contamination | Check curing temperature, improve pretreatment |
Color variation | Curing temperature fluctuation | Monitor oven temperature uniformity |
表格
Defect | Possible Cause | Solution |
|---|---|---|
Runs / sags | Excessive film thickness | Reduce spray output, increase flash-off time |
Cratering | Contamination or silicone residue | Improve cleaning, check air supply |
Poor gloss | Incorrect curing or solvent balance | Adjust curing temperature, check solvent blend |
Fish eyes | Oil or moisture contamination | Check air line filters, improve degreasing |
表格
Process Step | Critical Parameter | Target |
|---|---|---|
Powder material | Particle size D50 | 30-50 μm |
Spray distance | Distance from gun to part | 150-250 mm (optimal 200 mm) |
Electrostatic voltage | Voltage setting | 60-90 kV (flat parts 70-80 kV) |
Film thickness | Target thickness | 80-120 μm |
Curing temperature | Oven temperature | 180-200°C |
Adhesion | Cross-cut test | ≥ Grade 4 |
Color difference | Same batch ΔE | ≤ 1.0 |
表格
Process Step | Critical Parameter | Target |
|---|---|---|
Film thickness | Target thickness | 40-80 μm |
Flash-off time | Leveling time | 5-10 minutes |
Curing (bake) | Temperature × time | 80°C × 30 min |
Curing (air dry) | Temperature | 24h at room temp |
VOC compliance | Emission control | National standard |
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Contact DINGPRECISION for your metal spray painting needs. Our technical team is ready to support your product development, compliance verification, and quality assurance requirements.
Request a Custom IP-Rated Enclosure Quote
Phone: +1 3142997740
Email: niewenhui@dingprecision.com
Website: www.dingprecision.com
