Aluminum anode electrophoretic coating process management
Table 1 Anodic electrophoresis test items Project management scope Liquid temperature/°C 18~25 Solid fraction (%) 7~9 pH, 20°C 8.0~8.8 Resistivity/Ω·cm, 20°C 1500~2500 Amine value/mg 25~40 Acid value/mg 22~28 1 Several major factors and management methods affecting the anode electrophoresis In anode electrophoresis process, voltage, power-on time, the solid, an increase in the resistivity will promote the growth of the film thickness, the change of pH value on the contrary, the pH value increases, the thickness decreases, in order to effectively control the electrophoresis process, should Manage and control the above factors. 1.1 Solids: As the electrophoretic throughput increases, it must be continuously replenished. The size of the solid has a direct effect on the film thickness. Therefore, to ensure a uniform film thickness, the solid content should be controlled within ± 0.2%. 1.2 pH value: The aluminum anode electrophoresis is achieved by alkali or amine neutralization into salt to achieve a stable water-soluble system, its pH value between 7.5 to 9, in the electrophoresis process, negatively charged resin deposition On the work piece, at the same time, the amine is continuously generated on the cathode, and the pH of the paint gradually increases. In addition, if the electrophoretic bath is left for a long time, the pH will decrease due to the volatilization of the amine. The change of pH value will cause the change of electrodeposition characteristics and paint film. The pH value is too high and the coating film becomes thin. After the electrophoresis, the coating film will re-dissolve and result in insufficient film thickness and abnormal appearance of light loss; the pH value is too low and the electrophoresis tank Poor fluid stability. Therefore, the pH should be strictly controlled to ensure that it is within the process parameters. The pH of the anodized aluminum electrophoresis can be effectively controlled by the ion exchange resin method. 1.3 Resistivity: The resistivity varies with the amount of amine, the temperature, the solid content, and the amount of the amino resin and should be controlled in the range of 2000±500 Ω·cm. The change in the amount of amine affects the resistivity more than the pH. By regularly ion exchange treatment, excess amines and impurity ions are removed to maintain the resistivity in the normal range. 1.4 Amine value: The value of its value indicates the amount of amine in the electrophoretic fluid. The amine value increases as the electrophoretic throughput increases. The amine value can be reduced by ion exchange treatment. The size of the amine value is reflected in pH and resistivity, and is usually managed by controlling pH and resistivity. 1.5 Impurity ions: Impurities mainly consist of anions such as SO2-4, CO2-3, Cl-, and Na+, Mg+, and other metal cations, which are harmful to electrophoretic coating. The surface of aluminum profiles is easy to carry with SO2-4 due to the oxidative coloring process, and cleaning should be enhanced to avoid being carried into the electrophoresis tank. 2 Electrophoresis process pre-processing and post-washing process 2.1 Mixing tank and replenishment: Normally, the anode electrophoresis stock solution needs to be diluted and mixed into the electrophoresis tank and added every day. Deionized water is used for all diluted water. 2.2 Washing before electrophoresis: Use more than two times of water washing, and use pure water afterwards to ensure that the electrophoresis bath is not contaminated. 2.3 Washing after electrophoresis: After electrophoresis, there should be two or more times of water washing, and pure water washing should be used later. If RO device is adopted, RO closed system can be used macroscopically. After washing, there is preferably water absorption or dripping device. Compressed air or high-pressure air is used to blow the moisture on the surface of the profile and in the gap, and the water accumulated in the grooves by the tilting device is set. Because it is easy to produce water marks when dried on the surface, it affects the decorative properties. 2.4 RO Closed Circuit System The so-called RO reverse osmosis device is a pressure-driven reverse osmosis, seawater desalination, and dialysis are all based on the principle of reverse osmosis. Role of RO device: ·Recover electrophoretic coatings to improve the utilization rate of the paint, from the original 55% to more than 98%. · The permeate can be used as washing water to realize a closed loop system. · Reduced or no wastewater discharge is conducive to environmental protection. Since the water after RO is nearly pure water, it can be directly used for cleaning, so a closed-circuit washing system can be realized, which is beneficial to environmental protection. UVC lamp 253.7nm, different type. quartz material . Uvc Lamp,Uv Germicidal Bulb,Uv Germicidal Lamp,Uvc Tube Changxing leboom lighting product CO.Ltd. , https://www.leboomuv.com