Introduction to New Steel Drum Coating Applications
Hu Zongwei
1. Water-Based Drying Coating for Steel Drums
Composition: Water-based polyester resin, methyl etherified amino resin, pigments, functional fillers, additives, and water.
Application: Ideal for steel drums and metal components that can be baked at high temperatures.
Performance: Offers vibrant, glossy, and durable coatings with excellent weather resistance, moisture resistance, good application tolerance, and is environmentally friendly and non-toxic.
Application Process: The steel drum should be phosphated, washed, and dried before being sprayed. The residual heat of the drum must meet the temperature requirements of the water-based paint, making it suitable for color-filled drums and baking at 140°C for 17–20 minutes. The cleaned and dried drums must not have any oil or sweat residue.
For dark-colored coatings, a higher viscosity is required—typically around 50 seconds ± 5 seconds.
Main Technical Parameters:
- Paint film appearance: Smooth and uniform
- Fineness: ≤ 20 μm
- Viscosity: ≥ 90 s
- Drying time (at 140°C, 30 min): ≤ 30 min
- Gloss (60° meter): ≥ 90
- Hardness (pencil test): ≥ H
- Impact strength: ≥ 50 cm
- Adhesion: ≤ 1 (level)
- Flexibility: ≤ 2 mm
- Water resistance (40 ± 1°C): 24 hours without foaming; slight changes allowed after 2 hours with recovery.
2. High-Solid Drying Coating for Steel Drums
Composition: High-solid polyester resin, high-solid methyl etherified amino resin, active solvent, pigments, functional fillers, and additives.
Features: This coating contains up to 80% solid content, using an active solvent that reacts during baking to form a film without releasing volatile gases. The solvent is difficult to evaporate, making the process eco-friendly and nearly non-toxic. It performs similarly to UV-curable coatings and is encouraged by national policies as an environmentally friendly option. Compared to traditional products, it offers better fullness, larger coverage area, lower cost than water-based paints, and uses the same application method as conventional solvent-based coatings.
Main Technical Parameters:
- Gloss (60° meter): ≥ 90
- Solid content: ≥ 80%
- Hardness (H): ≥ 1
- Coverage area (dry film thickness 30μm): 20 m²/kg
- Impact strength (vertical drop hammer method): ≥ 50 kg/cm²
- Adhesion: ≤ 1 (level)
- Weather resistance (Tibet region, light loss and color change): ≤ 1
3. Light-Curing Coating for Steel Drums
Over the past decade, light-curing coatings have been widely applied in auto parts, metal components, plastics, and wood. These are environmentally friendly coatings supported by national policies.
The key feature is that the resin and active diluent in the coating rapidly crosslink under ultraviolet light from a high-pressure mercury lamp, forming a film without emitting volatile substances. The energy consumption is low, and the UV intensity is typically between 296–300 nm, with a working distance of 15–20 cm and a curing time of about 12 seconds.
Currently, light-curing coatings are best suited for lighter colors. Dark colors like black, dark blue, and iron red may not cure properly due to pigment interference with UV penetration, which can affect hardness. However, most other colors work well. The current ex-factory price is approximately 40 yuan per kilogram. The coating provides excellent fullness and significantly improves coverage over traditional paints. It can be sprayed and offers good color retention, making it a promising product for the steel drum industry.
Main Technical Parameters:
- Solid content: 100%
- Volatile matter: ≤ 0.5%
- Hardness (H): ≥ 2H
- Impact strength (vertical drop method): ≥ 50 kg/cm²
- Coverage area (dry film thickness 30μm): ≥ 20 m²/kg
- Gloss (60° meter): ≥ 90
- Adhesion: ≤ 1 (level)
- Weather resistance (12 months in Tibet, light loss and discoloration): ≤ 1
- Artificial aging (QUV, 60h, light loss and discoloration): ≤ 2
In summary, light-curing coatings do not require significant changes to existing equipment. Only two sets of high-pressure mercury lamps need to be installed in the drying tunnel, and the gas and fuel systems can be removed. Instead of relying on heat, the curing source is ultraviolet light, greatly reducing energy costs and eliminating environmental risks from volatile substances. These coatings are already widely used in the automotive and motorcycle industries, and their potential for adoption in the steel drum sector is very promising.
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