In the automobile manufacturing process, body painting is one of the most time-consuming and technically complex stages, as well as a major contributor to the "three wastes" (waste gas, waste water, and solid waste). Driven by automotive industry regulations and environmental concerns, reducing painting hazards, lowering coating costs, and improving coating quality have always been key focuses in coating technology development. Over the past decade, remarkable progress has been made in new materials, processes, and technologies, particularly in terms of quality, environmental protection, and cost efficiency. In addition to the widespread use of eco-friendly materials in the traditional three-layer coating system, innovative processes and technologies that were once considered unachievable are now being applied or are on the verge of implementation. This indicates that automotive body painting technology is entering a new phase of development.
First, the four essential elements of automotive paint booth operations—coating materials, processes, equipment, and management—are interdependent and collectively drive the advancement of coating technology. The 21st century is known as an era of environmental awareness, with sustainability becoming a top global priority. Automotive painting, especially for vehicle bodies and components, remains one of the most energy-intensive and polluting stages in the production cycle. As a result, minimizing pollution, cutting costs, and achieving high-quality finishes have remained central goals in the evolution of coating technology.
Second, wastewater generated from car painting booths poses a serious threat to the environment. Over the past ten years, coating technology and equipment have evolved significantly, focusing on the use of environmentally friendly materials, reduced wastewater and residue discharge, lower costs, and optimized production processes. Thanks to advancements in coating materials, the design of body coating systems has also seen revolutionary changes. Several new coating systems and technologies are either already in industrial use or will be soon, marking a shift toward more sustainable practices.
Third, several innovative coating processes are currently being used or explored in the automotive industry. These include reverse process technology, secondary electrophoresis, integrated coating, and membrane technology.
The reverse process involves applying powder coating to the outer surface of the body, followed by electrophoretic coating after melting, and then drying both layers together. This method can reduce electrophoretic coating usage by about 60%, replace the primer and intermediate layer with a 70μm thick powder coating, and eliminate the intermediate layer and its drying process, leading to significant savings in material and energy costs and a reduction in VOC emissions.
The secondary electrophoresis process uses two layers of electrophoretic material, with the second layer (35-40μm) replacing the intermediate coat. This approach offers high stability, reliability, and material efficiency, while requiring less equipment investment and eliminating the need for air conditioning. It can cut costs by 48% and reduce maintenance frequency and VOC emissions.
The integrated coating process replaces the intermediate coat with a functional layer (15μm) that matches the topcoat color, eliminating the need for drying between layers and removing the intermediate coat line. This not only reduces VOC emissions but also improves production efficiency.
Membrane technology involves pre-fabricated topcoat films suitable for thermoforming. The resulting finish closely resembles conventional spray coatings. This technology is mainly used for plastic parts, where the film is molded along with the part using insert molding or in-mold techniques, creating a defect-free finish.
In this setup, the body frame is manufactured through traditional stamping and welding, and only the frame is painted. A powder coating is used for the top layer, and since the exposed area is small, the color doesn't need to match the cover. Large covers, made of plastic via film coating, come in thousands of colors, simplifying the painting process and reducing costs. VOC emissions are kept below 7g/m², far below European standards.
Currently, developed countries like the U.S. and Europe are rapidly adopting eco-friendly materials in their body painting processes, with VOC emissions well below the strictest regulations. Coating automation, production efficiency, and material utilization rates have improved further, and new technologies aimed at reducing costs and emissions are emerging and being implemented. These innovations are no longer limited to traditional processes; alternative methods are being applied or are on the horizon.
This transformation is reshaping the design and manufacturing concepts of traditional automotive bodies, making the coating process simpler and more efficient. While China's current body painting technology is not too different from that of Europe and the U.S., there is still a gap in research and development of coating materials and related technologies. Addressing this gap is a shared challenge across the industry.
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