Water-based paint is a new type of environmentally friendly coating developed for environmental protection and personal safety. However, it is undeniable that its application in industrial fields such as motors is still somewhat unsuitable. Nevertheless, water-based paint has become one of the materials that motor manufacturers must choose.
"What's the purpose of all this extra equipment over there? It looks like it was newly added." Ms. Can, passing by a large facility for spraying surface paint at a certain company, noticed the obvious signs of splicing and couldn't help but ask the company's guide accompanying her on the tour. "These are additional equipment added for environmental upgrades! The factory has upgraded all its spraying equipment. If a water-based paint production line is implemented, the working conditions for the operators and the factory's environmental standards will be raised to a new level," the guide explained.
"Water-based paint!" Those words sound so familiar. Ms. Can, who has always considered water-based paints for home decoration, is about to be seen in factories. It seems that replacing oil-based paints with water-based paints in industrial applications isn't just a theoretical exercise; powerful manufacturers are already planning and implementing it.
What are the advantages of water-based paint?
● Improved environmental protection and resource utilization. Water-based paints use water as a solvent, saving a significant amount of resources; the risk of fire during application is reduced, and air pollution is decreased; water-based paints use only a small amount of low-toxicity alcohol ether organic solvents, thus effectively improving the painting environment.
● It has strong adaptability to the substrate. Water-based coatings can be applied directly to wet surfaces and in humid environments; they have good adaptability to material surfaces and strong coating adhesion.
● Painting tools are relatively easy to clean. Spraying tools can be cleaned with water, greatly reducing the consumption of cleaning solvents and also reducing pollution to people and the environment.
● Electrophoretic coating can be used. After electrophoretic coating, the coating film has good flatness; a certain thickness of coating film can be applied to the inner cavity, weld seam, corner and edge parts, which has good protection; the electrophoretic coating film has the best corrosion resistance, and the salt spray resistance of the thick film cathodic electrophoretic coating can reach up to 1200h.
What is electrophoretic coating?
Electro-coating is a coating method that uses an external electric field to cause pigments and resin particles suspended in an electrophoretic solution to migrate directionally and deposit onto the surface of a substrate, which is one of the electrodes. The principle of electro-coating was invented in the late 1930s, but its development and industrial application only began after 1963. Electro-coating is a special film-forming method that has developed over the past 30 years and is the most practically significant construction process for water-based coatings. It features water solubility, non-toxicity, and ease of automation, and has rapidly gained widespread application in industries such as automotive, building materials, hardware, and home appliances.
Characteristics of water-based paints and precautions for their application
As the name suggests, water-based paints contain water and are water-soluble. When using them, appropriate measures must be taken to address this characteristic.
●High cleanliness requirements. Due to the high surface tension of water, dirt can easily cause pinholes in the coating film. Therefore, water-based coatings require a high degree of cleanliness during the application process and on the surface of the material.
● High requirements for delivery pipelines. The pipelines must be of good shape and free of defects. Because water-based coatings have poor dispersion stability against strong mechanical forces, when the flow rate changes drastically, the dispersed particles are easily compressed into solid particles, causing pitting in the coating film. ● High equipment cost. Water-based paint coating equipment is highly corrosive, requiring corrosion-resistant linings or stainless steel materials. Corrosion of the delivery pipeline by water-based coatings can cause metal dissolution, leading to the precipitation of dispersed particles and pitting in the coating film; therefore, stainless steel pipes are also necessary. ● Complex drying process. Baking-type water-based paints have stricter requirements for the application environment, increasing the need for temperature and humidity control equipment and thus increasing energy consumption. Compared to oil-based paints, water-based baking consumes significantly more energy.
● Water-based paints have poor water resistance. Water-based coatings are generally slightly alkaline, which affects the stability of the coating and the performance of the film.
● Electrical conductivity. The resistance of water-based paint does not exceed 0.1MΩ, while the resistance of solvent-based paint is between 0.5 and 20MΩ. Water-based paint cannot be used in special applications.
●Corrosive. Water-based paints contain a large amount of water, and therefore are corrosive to moisture-prone parts such as containers, pipelines, and spray booths.
● Rheological behavior. The English translation of "rheological behavior" is rheological behavior; in academic literature, "rheological behavior" is defined as the deformation behavior of polymers in a viscous flow state.
Key points of water-based paint application technology
● Poor dispersibility. Water-based paints are polymer dispersion systems, and their pigment dispersibility is relatively poor. Measures should be taken to improve this. Many water-based paint manufacturers have already solved this problem.
● The dispersed particles have poor stability. They are easily destroyed by shear forces; therefore, shear forces should be avoided during the manufacturing and transportation of water-based paints.
● The dispersed particles are sensitive to acidic substances. The presence of acidic substances in the paint will form acidic particles, leading to gelation and damage to the water-based paint. Furthermore, the dispersed particles of water-based paint will also be damaged if it freezes during transportation.
●Surface tension issues. Water-based paints have a high surface tension, so management must be strengthened during construction. Otherwise, the following defects and paint film problems are likely to occur during coating: (1) sagging; (2) poor leveling; (3) pinholes and craters; (4) difficulty in penetrating into small cracks on the coated surface; (5) difficulty in drying, and greatly affected by ambient temperature and humidity.
Application Trends of Water-Based Paints in the Motor Industry
Water-based paint is a new type of environmentally friendly coating developed for environmental protection and personal safety. However, its application in industrial fields such as motors is undeniably somewhat unsuitable. Nevertheless, water-based paint has become one of the essential materials for motor manufacturers. How to achieve its rapid and effective widespread application is a problem that water-based paint manufacturers must address. Whether it's surface paint for motors or winding impregnation paint, the appropriate spraying and baking processes are also practical issues that motor manufacturers must face. In solvent-based paints, 50% of the total solvent evaporates during the spraying and atomization process, while for water-based paints, only 25%. Slow water evaporation easily leads to sagging during coating and reduces coating efficiency. Therefore, an intermediate heating zone is needed to forcefully evaporate water from the water-based primer coating.
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