Qingguo Intelligent is a leading China Electrophoresis Production Line manufacturer. Electrophoretic production line and coating electrophoretic treatment process are advanced surface treatment technologies mainly used to form uniform and high-quality coatings on conductive materials such as metals. Here is a detailed introduction:
Electrophoretic coating is a coating method that uses an external electric field to induce the directed migration and deposition of pigments, resins, and other particles suspended in an electrophoretic solution onto the surface of an electrode. In the electrophoresis process, the coated material serves as the cathode (or anode), and the electrophoretic coating is cationic (or anionic). Taking cathodic electrophoresis as an example, when the power is turned on, positively charged coating particles move towards the surface of the workpiece as the cathode under the action of an electric field, and discharge and deposit on the surface of the workpiece to form a coating. This process is similar to electroplating, but electroplating mainly involves depositing metals, while electrophoresis involves depositing organic coatings.
Surface pretreatment
Purpose: To ensure that the surface of the workpiece is clean, free of oil stains, rust, and other impurities, providing a good substrate for electrophoretic coating. Because if there are pollutants on the surface of the workpiece, it will affect the adhesion and quality of the electrophoretic coating.
Method
Degreasing: Use alkaline degreasing agents or organic solvents to remove grease from the surface of the workpiece. For example, for automotive body stamping parts, alkaline degreasers are commonly soaked or sprayed at a certain temperature to remove lubricating oil contaminated during the stamping process.
Acid washing: Use acid solution (such as hydrochloric acid, sulfuric acid) to remove rust and oxide scale. But after acid washing, sufficient water washing is needed to prevent acid residue.
Phosphating (or passivation): Phosphating treatment forms a layer of phosphate conversion film on the surface of the workpiece, which can improve the adhesion and corrosion resistance of the electrophoretic coating. Passivation is the formation of a very thin protective film on the metal surface, which also plays a similar role. For example, before electrophoretic coating on some hardware components, zinc based phosphating treatment can be carried out to generate a phosphating film that can better adhere to the electrophoretic coating.
Electrophoretic coating
Preparation of electrophoresis tank solution: Prepare the electrophoresis coating into the electrophoresis tank solution according to the specified ratio and process requirements. The composition of the tank solution includes resin, pigment, solvent, additives, etc. Its parameters such as solid content, pH value, conductivity, etc. need to be strictly controlled. For example, the solid content of cathodic electrophoretic coatings is generally between 18% and 25%, and the pH value is around 5.8-6.7.
Coating operation: Immerse the pre treated workpiece into an electrophoresis tank, turn on the power, and perform electrophoresis coating. Coating voltage, time, and current density are key parameters. Generally speaking, the voltage is between 150-350V, the coating time is 2-3 minutes, and the current density varies depending on factors such as the shape and size of the workpiece. For example, in electrophoretic coating of automotive parts, by precisely controlling these parameters, the coating can be evenly deposited on the surface of complex shaped parts.
After cleaning
Purpose: To remove residual electrophoretic paint and other impurities on the surface of the workpiece after electrophoresis. If not cleaned thoroughly, residual paint may form defects such as flow marks after drying.
Process: Typically, multi-stage water washing is used, including ultrafiltration washing and pure water washing. Ultrafiltration water washing is the use of ultrafiltration devices to recover electrophoretic paint while cleaning workpieces; Pure water washing is to further clean the workpiece with deionized water. For example, in some large electrophoretic coating production lines, workpieces need to undergo 3-4 levels of water washing to ensure cleaning effectiveness.
Drying and solidification
Purpose: To cure the resin in the electrophoretic coating to form a hard, wear-resistant, and corrosion-resistant coating. Drying temperature and time are important factors affecting the performance of coatings.
Operation: Generally, hot air circulation drying furnace or infrared drying furnace is used for drying. For cathodic electrophoretic coatings, the drying temperature is usually between 160-180 ℃ and the drying time is 20-30 minutes. Different coating systems and workpiece sizes may adjust the drying parameters. For example, the drying temperature of some small hardware components can be appropriately reduced and the time can be shortened, but it is necessary to ensure that the coating can be fully cured.
High coating quality
Good uniformity: As electrophoretic coating is carried out under the action of an electric field, coating particles can be uniformly deposited on various surfaces of the workpiece, including complex shaped cavities, gaps, and other areas. For example, in the electrophoretic coating of car frames, even the internal tube structure of the frame can be uniformly coated, which is difficult to achieve with other coating methods such as spraying.
Strong adhesion: The electrophoretic coating has good adhesion to the pre treated metal surface, thanks to the conversion film formed during the pre-treatment process and the chemical properties of the electrophoretic coating. This strong adhesion makes the coating less likely to peel off during use, improving the durability of the product.
Superior environmental performance
Less organic solvent volatilization: The content of organic solvents in electrophoretic coatings is relatively low, and the amount of organic solvent volatilization during the coating process is small, reducing air pollution. Compared with traditional solvent based coating spraying, electrophoretic coating can reduce VOC (volatile organic compound) emissions by 70% -90%.
High utilization rate of coatings: During the electrophoretic coating process, most of the coatings that have not been deposited on the surface of the workpiece can be recovered through ultrafiltration devices, with a coating utilization rate of up to 90% -95%, reducing coating waste and processing costs.
High production efficiency
High degree of automation: The electrophoretic coating process is easy to achieve automated production, and the workpieces can be transported to various workstations for processing through an automated conveying system, reducing manual operations and improving production speed and product quality stability. For example, in the production of large household appliance casings, the use of electrophoretic coating automated production lines can quickly and efficiently process a large number of workpieces.
Automotive industry
Almost all car bodies, frames, components, etc. use electrophoretic coating as a primer. It provides excellent anti-corrosion performance for cars and extends their service life. For example, the coating thickness of modern car body electrophoretic primer is generally between 20-30 μ m, which can effectively resist corrosion factors such as salt spray and rainwater during road driving.
Home appliance industry
Used for coating the shells of household appliances such as washing machines, refrigerators, and air conditioners. Electrophoretic coating can give home appliance shells a good appearance and corrosion resistance, while meeting environmental requirements. For example, the shells of some high-end washing machines are coated with color electrophoretic coating, which is both beautiful and durable.
Hardware products industry
Paint hardware tools, building hardware and other products. It can improve the decorative and corrosion resistance of hardware products, for example, in the electrophoretic coating of hardware tool handles, it can make the handle surface have a comfortable touch and good anti slip performance.
