Coating materials, coating technology, painting equipment, painting management is the four elements of automotive coating, complement each other to promote the coating process and technology progress and development. In the 21st century, which is called the environment-oriented new century, environmental protection has attracted worldwide attention and has become the most urgent research topic for mankind. Automotive and its parts and components of the automobile manufacturing process is the highest energy consumption and waste generated one of the most. Therefore, to reduce the coating pollution, reduce coating costs, improve the quality of painting has been the subject of coating technology.

I. The application of new coating materials

The application of new coating materials is the forerunner of the progress of coating technology. Under the premise of satisfying the requirement of coating performance, it is the main development target to reduce the pollution and reduce the coating cost.

In this case,Free degreasing agent, non-nickel phosphating solution, non-nitrite phosphating solution, chromium-free passivating agent, low-temperature degreasing agent (treatment temperature 43 ℃), the same low temperature Low temperature (160 ℃ 10min), low heating loss (4 or less), low VOC volatile (0.4 ~ 0.8) type, low sulfur content (0.4 ~ 0.8), low slag (lower than conventional 10 ~ 30) phosphating solution, lead-free Wuxi cathodic electrophoretic coating and low temperature curing Cathodic electrophoretic coating in Europe and the United States and Japan has been promoting the use of many years.

In Europe, some automotive companies have adopted new waterborne coatings in recent years, with VOC emissions below 35 g / m2 (Germany TA-Luft, 1995). From the beginning of the 1990s, all new paint line primer used in all the electrophoretic primer or powder coating, coating with water-based paint or high-solid materials, paint with water-based background plus high solid varnish. At present, the powder varnish has been applied to car body coating. Following the industrial application of powder varnish, the powder metal background has also been commercialized.

In North America, powder coating has been industrialized for many years, while water-based paint in recent years, very popular background, high-solid coating and topcoat application is also quite common. Europe and the United States of ultraviolet (UV) curing coating in the automotive coating technology is close to maturity. Japan is also actively developing and promoting water-based coatings, high solids and ultra-high solids paint finish. In this case,With the global environment deteriorating, we must significantly improve the acid rain resistance and abrasion resistance of automotive coatings.

In recent years, the electrophoretic coating with low swell, low pigment content, anti-acid rain and anti-abrasion topcoat, multicolor midcoat and viscosity control coating have been widely used to reduce the difference of film thickness between the inner and outer surface of the car body. application. China's major automobile companies in the paint before the processing of materials and application of electrophoretic paint with the international level or less, but the application of water-based intermediate coating and water-based paint must use special equipment, thus increasing the coating costs.

Although foreign-owned and joint ventures have the capability to produce water-borne intermediate and water-based topcoats in China, traditional automotive coatings and topcoats use traditional low- and medium-solid solvent-based paints. VOC emissions are far behind Europe.

2. Painting process and equipment

Over the past decade, the progress of the coating process and equipment is mainly reflected in the application of environmentally friendly coating materials, reducing waste water, waste emissions, reduce costs, optimize the automobile production process and so on. As the coating material progress, body coating system design has also been a revolutionary progress, several typical new coating system and new technology has been or will soon be used for industrial production. China's current coating technology and equipment is generally equivalent to the level of 10 years ago in Europe and America, some companies in the new coating line with some of today's international advanced level of new equipment.

2-1. Water-saving and waste recycling technology

Pretreatment and electrophoresis are the most important link in water consumption and waste water discharge. Membrane separation technology (UF and RO) is used to recover the degreasing liquid, regenerated cleaning water and pretreatment wastewater, which makes the real-time electrophoresis closed-circuit cleaning possible. At present, the membrane separation technology has already begun to apply.

In recent years, with the industrialization of environmental protection coatings developed countries, some of the coating recycling technology (such as powder slurry recycling technology, powder and varnish recycling technology, waste paint flocculation dryer technology, ultrafiltration, cooling And electrostatic adsorption recovery of water-based paint technology, spray paint water-based paint paint recycling technology, etc.) has also been applied, so that the paint line to further improve the utilization of paint, to minimize the waste paint residue emissions.

At present, China's water-saving and comprehensive utilization of waste in the attention is not enough, in the application of new technologies is relatively backward.

2-2. Several new body coating process

Reverse process: in the outer surface of the body powder coating spray, hot melt and then electrophoresis coating, followed by powder / electrophoresis coating with drying. The use of this process can reduce the amount of about 60 of the electrophoretic coating, with a thickness of 70m powder coating to replace the outer surface of the electrophoretic primer and the coating, the abolition of coating and drying process, thereby saving materials and energy costs, lower VOC emissions.

Secondary Electrophoresis: Two-layer electrophoresis was used, and the second layer electrophoresis (35-40 m) was used to replace the middle coating. High reliability, high qualified rate, high material utilization, less equipment investment (no need of air conditioning system), saving cost 48, reducing the frequency of repair and the traditional paint and VOC emissions in the coating process of automation and stability.

Integrated coating process (three coating concept): the same color with the top layer of the functional layer (15m) instead of the coating, the functional layer and the paint between the bottom without drying, cancel the coating line, to improve production efficiency At the same time, a significant reduction in VOC emissions.

2-3. Film coating technology instead of plastic coating

The topcoat technology is a preformed topcoat film that is thermoformed. The topcoat properties and appearance of thermoformed products are very similar to those of conventional baking spray coatings. The technology is mainly used in the production of plastic parts, the use of folder molding or internal mold process will be prefabricated composite film in the plastic part of the casting at the same time forming and forming with the plastic parts to be non-defective coating cover. Body skeleton using the traditional stamping welding process manufacturing, painting shop only on the body frame coating, topcoat powder coating technology. Because body skeleton exposed area is smaller, so the topcoat color and cover the same, the depth of 1 can. Large area of the cover are made of plastic film technology, there are thousands of colors.

This greatly simplifies the body coating process, while reducing coating costs, so that the coating VOC emissions to 7g / m2 or so, far below the requirements of the European emission regulations.

2-4. Body painting P2ZERO concept

The so-called P2Zero concept is zero-emission paint shop. To meet the harsh environmental requirements and user quality requirements under the premise of reducing the cost of waste treatment, reduce paint shop operating costs and simplify the paint process. Anti-corrosive primer coating of the steel plate of the automobile body is made before the parts are made, and the body of the paint shop does not need to be coated with the primer again.

Only a powder background and a powder coating are sprayed, thus minimizing the process waiting time, Eliminate the traditional paint, process adjustment more flexible, from the steel plate to paint the body before the elimination of rust production process, the complete elimination of traditional coating weld and cavity structure of the poor anti-corrosion problems, saving coating shop area, reduce No waste, no waste, no waste, no waste gas, no waste, no waste, no waste, no waste, no waste, no waste.

2-5. Chassis parts painting

In developed countries, the chassis parts coating commonly used phosphating, cathodic electrophoresis or powder coating process, the general assembly is generally the first part of the electrophoresis or powder coating, and then assembly, according to the need to spray coating on low temperature or room temperature curing paint . As the cathode electrophoresis and powder coating has good mechanical properties, some parts of the mechanical processing can be carried out after painting, so as to avoid parts in the coating before the long processing time and corrosion. Frame, chassis parts are mostly hot-rolled sheet and castings, forming or painting before the use of shot peening or blasting, pickling treatment has gradually been eliminated.

At present, China's parts painting production scale is generally small, generally relatively backward. Cars and other small passenger cars is relatively good, trucks, buses, agricultural vehicles, the coating process and the use of paint levels are not high.

2-6. New coating conveyor

Domestic current body coating line pretreatment and electrophoresis using a typical transport aircraft putt catenary, pendulum chain and program-controlled gourd. They have their own advantages and disadvantages, the common drawback is that the body can not solve many internal cavity structure of the effective exhaust problems, especially in the roof of the airbag problem. These sites can not be phosphate and electrophoresis treatment. The new multifunctional shuttle Vario-Shuttle and RoDip not only solved these problems, but also inherited all the advantages of the aforementioned transport aircraft.

Multi-function shuttle also has a production line in a variety of different processes to achieve the function, in full compliance with the requirements of automated flexible coating production. These two transport aircraft in the domestic new body coating line has begun to use.

2-7. Other coating equipment structure and function improvement

In Europe, coating equipment, structural materials to stainless steel-based, electrical equipment lines are designed in the device structure, the abolition of the electrical piping, equipment, modular design and workshop layout of the three-dimensional partition, to ensure maximum coating High cleanliness requirements and safety fire safety requirements. No external air duct and internal radiation to strengthen the convection of a new generation of drying room, a substantial increase in thermal efficiency and drying temperature uniformity. With the advancement of robot technology, the body automatic coating machine is gradually replaced by multi-degree of freedom of the spraying robot, spraying and sealing a large number of automatic use of the robot than the coating machine is more flexible to adapt to production. Mechanized transmission chain commonly used non-metallic materials, a significant reduction in transmission noise.

3.Painting management

Painting management, including orders for coating materials, material quality control and construction process control and so on. Because of the variety of materials used in automobile coating, it is easy to deteriorate in the process of storage and transportation, the process is long, the parameters need to be controlled and so on, which is the most complicated in the automobile production management. In the automotive industry developed countries, the development of automotive coating materials to promote the progress of automotive coating technology, in order to reduce the cost of painting, supply from a single material supply system for the transition to supply. System delivery methods began in the early 1990s, now in Europe and the United States has been basically universal. The world's major automobile manufacturers have always attached great importance to the painting management, coating manufacturers directly responsible for the production and technical management of the coating, so that automobile production plant management greatly simplified coating, painting a pass rate, lower production costs. At present, this management approach in the domestic automobile companies are still in the trial stage.

In recent years, some of the strength of the coating materials and coating equipment company has launched a BOT service model, the car company's painting shop by the coating materials company or coating equipment company to invest in construction and production management, according to Automobile production company plans to paint production, supply of automotive companies is a qualified coating. Automotive companies only need to develop technical standards and inspection supervision coating product quality. This will become a major trend in coating management.

China's auto coating technology and the international level of the gap is shrinking, but the development is still uneven, the coating quality assurance, several major car manufacturers have reached international standards, but the comprehensive comparison is still about 10 years gap, Mainly in cleaner production technology; automotive coating production of key equipment technology, China may in the future for a long period of time mainly dependent on imports. China is expected in the next 10 to 15 years, the automotive coating level will be fully integrated with international practice, speed up the conservation of resources and environmental technology applications.