Special Equipment Powder Coating Line
Specialized Equipment Powder Coating Line -– Maersk Container Coating Project
In the Maersk container coating project, the production line is designed for standard containers and large steel structural components, addressing key requirements such as large workpiece dimensions, stable batch production, and high corrosion resistance.
To withstand harsh marine environments—including high salinity, humidity, and long-term outdoor exposure—the line has been systematically optimized based on conventional powder coating technology.
The project adopts a process route of “enhanced pretreatment + electrostatic powder coating + high-efficiency curing,” combined with a “floor-mounted chain conveyor + programmable hoist transfer” system. This configuration enables automatic transfer between loading, pretreatment, and subsequent processes, reducing manual intervention while ensuring stable production rhythm and continuous operation.
Process Flow
1. Loading & Conveying System
In this project, a combination of floor-mounted chain conveyor and programmable hoist transfer system is used to achieve grouped loading and automatic transfer to the pretreatment and e-coating sections.
Through precise transfer control, workpieces move smoothly between different conveying systems, minimizing uncertainties caused by manual handling while ensuring stable production flow, improved efficiency, and reliable operation.
2. Pretreatment & Surface Treatment
For large container steel structures, a combined spray and immersion pretreatment process is adopted.
The degreasing stage utilizes an external hot water indirect heating system, maintaining process temperatures steadily within the range of 40–50°C. This effectively prevents localized overheating and ensures stable process conditions for both the workpieces and treatment baths, providing a reliable foundation for subsequent coating operations.
In addition, the pretreatment section incorporates a multi-stage counterflow rinsing and water recycling system, including counterflow cascading between pre-degreasing and main degreasing tanks, as well as counterflow DI water rinsing. This design significantly reduces water consumption while improving chemical utilization, achieving both energy savings and operational efficiency.
To enhance production flexibility, the line is designed to accommodate both standard containers and dump truck bodies. Capacity is also reserved for a waterless four-in-one phosphate-free conversion coating process, enabling mixed production of different product types and improving overall line utilization.
3. Drying
After pretreatment, the workpieces enter a hot air circulation drying system to completely remove residual surface moisture.
By optimizing temperature profiles and airflow distribution, uniform drying is achieved across all areas of large structural components, preventing moisture-related coating defects in subsequent processes.
4. Powder Coating
The coating stage adopts electrostatic powder coating technology combined with automatic spraying and manual touch-up to meet the coating requirements of large-area and complex container structures.
Through optimized spray gun layout and electrostatic parameters, uniform coverage is achieved across large surfaces. Critical areas such as edges and weld seams are reinforced through manual touch-up to ensure consistent coating thickness and protective performance.
The coating system is synchronized with the conveying system rhythm, maintaining stable coating quality and high powder utilization during continuous production.
5. Powder Curing
After coating, the workpieces enter a large-capacity curing oven for thermal curing.
Using a hot air circulation system with optimized temperature distribution and curing profiles, the powder coating fully melts and cross-links, resulting in excellent adhesion, mechanical strength, and corrosion resistance suitable for long-term marine exposure.
6. Cooling & Conveying
After curing, the workpieces pass through a cooling zone using either natural cooling or forced cooling to stabilize the coating.
The finished workpieces are then transferred via the conveying system to the unloading area. Flexible loading and unloading arrangements enable efficient handling of different product sizes and production volumes.
