Report on spray plastic surface treatment technology —— High cost-effective anti-corrosion decoration solution
I. Function and Problem Solving
1. Core functions
- Long-term corrosion resistance: form 60-120μm epoxy/polyester coating, salt spray test up to 240-1000 hours (ordinary spray paint only 72-200 hours)
- Strong decorative: support 2000+ Pantone color code, surface texture can be selected smooth, orange, metal gloss
- Electrical insulation: breakdown voltage>30kV/mm, protect the shell of electrical equipment
- Environmental safety: no solvent volatilization (VOC=0), in line with RoHS/REACH directive
2. Pain point solution
| Industry pain points | Spray molding solution |
| Outdoor equipment is corroded and fails | The film thickness is>80μm and anti-ultraviolet aging |
| Complex workpiece coverage is uneven | Electrostatic adsorption achieves full coverage of dead corners |
| Traditional paint sagging pollution | Powder recovery rate>95% |
II. Working Principle
1. Dual mechanism of electrostatic adsorption and thermal curing
2. Micro film forming process:
① Powder charging → ② directional adsorption → ③ melt leveling → ④ crosslinking curing → ⑤, forming closed cell structure
(Figure: working principle of electrostatic powder coating (charged powder adsorption + high temperature curing))
III. Process operation process
Standardized operations
1. Pre-treatment (60% by mass)
• De-fatting (alkaline solution, 50℃×8min) → water washing → phosphating (zinc-based membrane weight 1.5-3g/㎡) → pure water washing → 120℃ drying
2. Electrostatic spraying
- • Equipment: high voltage electrostatic spray gun (output voltage-70kV)
- • Parameters: air pressure 0.5MPa, distance from the workpiece 200-300mm, film thickness control ±10μm
3. Curing and baking
- • temperature curve ：
- indoor temperature (10min) → 180°C (20min) → heat preservation (10min) → cooling
4. Quality inspection standards
- • Adhesion: scratch method (ASTM D3359) 0 grade qualified
- • Thickness: eddy current thickness gauge ≥60μm
IV. Comparison with other processes
| Characteristic | Spray plastics | Spray paint | Electrogalvanizing |
| Anti-corrosion life | 5-8 years (outdoors) | 1-3 years | 3-5 years (no passivation) |
| Environmental protection | Zero VOC emissions | Benzene solvent volatilization | chromate waste water |
| Color selection | More than 2000 Pantone colors | More than 500 colors | Silver-white/colored passivation only |
| Corner coverage | ＞95% | 70-85% | <50% (screening effect) |
| Composite cost | ¥25-50/㎡ | ¥15-30/㎡ | ¥20-40/㎡ |
Typical case ：
Communication cabinet (spray plastic): RAL7035 gray is selected, the film thickness is 80μm, and the salt spray test is 480h without corrosion
Painted parts of the same specification: 200h bubble, cost is low 30%, but life is short 60%
V. Application scenario recommendation
• Preferred scenario:
- ✅ Outdoor equipment (power distribution box/5G cabinet)
- ✅ Household appliances (refrigerator panels/air conditioning casings)
- ✅ Colored structural parts (shelves/exhibition tools)
• Use scenarios with caution:
- ❌ >200℃ high temperature environment (epoxy resin yellowing)
- ❌ Strong acid immersion condition (acid and alkali resistance is weaker than electrophoresis)
Conclusion: Spray coating has become the gold standard of iron plate corrosion protection with three advantages of environmental protection, decoration and coverage. Mingli Metal is equipped with an automatic spray coating line and a rapid color change system (<30min), which can provide enterprises with one-stop solutions from selection to mass production.
Append: spray plastic process chain real scene
Figure: fully automatic spray plastic production line (pre-treatment → electrostatic room → curing furnace)