The working environment of the satellite receiving antenna is relatively harsh, and the anti-corrosion requirements for the coating are relatively high. Our company adopts the receiving antenna after anodic electrophoresis coating, and the corrosion resistance is obviously improved. The salt spray resistance of the coating can reach more than 500 hours, prolonging its service life. At the same time, due to the improvement of production efficiency, the electrophoretic coating cost is 4 yuan lower than the original powder coating cost square meter, which improves the economic benefit.
2. Anode electrophoretic coating processThe satellite receiving antenna anodic electrophoretic coating process is as follows: pre-cleaning the surface of the workpiece release agent, pre-treatment, electrophoretic coating, post-cleaning, baking.
Process: upper part → pre-cleaning workpiece surface release agent (manual) → hot water wash (spray, 120 seconds, 40 ~ 60 ° C, tap water) → degreasing (spray, 120 seconds, 40 ~ 60 ° C, cleaning agent and Tap water)→Washing 1 (immersion, 60 seconds, normal temperature, tap water)→Washing 2 (spraying, 35 seconds, normal temperature, tap water)→washing 3 (spraying, 35 seconds, normal temperature, tap water)→pure water washing 1 (spraying , 35 seconds, normal temperature, pure water conductivity "20μs / cm" → pure water wash 2 (spray, 35 seconds, normal temperature, pure water conductivity "20μs / cm" → drain (100 seconds, with reserved water blowing station → anodic electrophoretic coating (immersion, 180 seconds, 25 ~ 30 ° C voltage 0 ~ 300V adjustable, solid content 12.5%, PH value 8.0 ~ 8.5, coating thickness 20μm ± 5) → UF liquid rinse on the tank → UF Liquid washing 1 (spraying, 35 seconds, normal temperature, UF liquid) → UF liquid washing 2 (spraying, 35 seconds, normal temperature, UF liquid) → pure water washing 3 (immersion, 60 seconds, normal temperature, pure water conductivity "20μs /cm)→Pure water wash 4 (spray, fresh pure water, straight discharge, counter-flow to pure water wash 3 tanks) → drain (180 seconds) → blow water (120 seconds, labor) → Bake (30 min, 170 ~ 180 ℃, direct-fired gas heating stove) → → the cooling member
Description:
(1) The filter system adopts 4 mesh bag structure, a total of 6 sets, 24 inner bag, and a filter bag with a hole diameter of 50 μm; not only meets the quality requirements of the paint film, but also prevents the filter bag from clogging.
(2) The circulatory system includes three aspects: 1) bath circulation 2) heat exchange cycle 3) ultrafiltration cycle. Since the flow rate and flow rate change have a great influence on the stability of the bath, the aging speed, the energy consumption, the bath foam and the quality of the paint film, the number of cycles of the anode electrophoresis bath is 5-7 times/hour.
(3) Control parameters of ultrafiltration system: inlet pressure: 0.35~0.40MPa, outlet pressure: 0.15~0.20MPa; ultrafiltration system operation should be continuous operation, intermittent operation is prohibited, to prevent the ultrafiltration membrane from drying out. In order to ensure that the ultrafiltration membrane is cleaned, a separate cleaning system is provided.
(4) The power supply system is energized into the slot of the two-stage power-on mode.
3, anode electrophoresis coating process parameter control3.1 voltage
In the electrophoresis system, the power-on mode is “in-slot energizationâ€, and the power-on mode is “two-stage power-on modeâ€. The surface coating of the satellite receiving antenna should not be too thick, otherwise it will affect the receiving effect. If it is too thin, it will affect the anti-corrosion performance and shorten the service life. On the specific electrophoresis line, the electrophoresis time of the workpiece is generally fixed. The thickness of the coating film is mainly controlled by the adjustment voltage. Because the surface area of ​​the satellite receiving antenna is relatively large, the power supply is segmented, and the workpiece is placed in the slot with a low voltage of 60-100V. The electrophoretic paint film on the workpiece is continuously formed, the resistance of the paint film will gradually increase, the current will decrease accordingly, and the electrophoresis effect begins to decrease. At this time, a high voltage of 150-250V is used to accelerate the deposition speed and evenly thicken the paint film.
3.2 bath conductivity
The conductivity of the electrophoretic paint liquid directly affects the quality of the satellite receiving antenna coating. If the conductivity is too high, the movement and electrification ability of the paint liquid particles will be enhanced, the electrolysis reaction will be accelerated, the paint film will become rough, and the conductivity will be too low. The liquid resistance increases and the current becomes small, which affects the throwing power and the adhesion of the paint film. The conductivity of the bath depends on the content of solids and impurity ions. Therefore, the pure water replacement liquid collection method is used to control the conductivity during operation so as to be in the normal working range.
3.3 bath temperature
If the temperature of the bath is too high and the deposition amount is too fast, the film will be rough and pores, causing damage to the paint film and accelerating the deterioration of the aqueous solution of the organic substance, affecting the stability of the bath, and the temperature of the bath will be too low. The film becomes thinner and the viscosity increases, and the bubbles on the surface of the object to be coated are not easily discharged, and the pores of the paint film are also roughened. At the same time, the swimming penetration decreased. The electrophoresis wire bath liquid temperature control system adopts the freezing system and the tank liquid electric control to automatically control the temperature.
3.4 electrophoresis time
Once the painting time is set, it generally does not change. If you want to change the production efficiency, you must change the line speed, which will cause the swimming time to change. The bathing time has a direct effect on the film thickness and the throwing power. Although the long time will increase the penetrating power of the paint, it will make the film too thick, increase the production cost, and the use effect of the satellite receiving antenna will also be worse. If the bathing time is too short, the film thickness will not be required, which will reduce the coating's anti-corrosion performance.
3.5 PH value
The anodic electrophoretic paint is an alkaline solution system, and it is necessary to rely on an appropriate amount of alkalinity to maintain the steady state of the paint liquid. When the pH value is too low, insoluble particles (dirt) will be produced, and the quality of the paint film will be deteriorated; when the pH value is too high, the electrodeposition amount and the dissolution balance of the paint liquid will be destroyed, and the paint film will also become thin, affecting the paint. Film quality.
3.6 Solids
The solid content of the bath refers to the content of film-forming substances (resins, pigments, additives, etc.) in the electrophoresis bath. The solid content is too high, the electrophoresis speed is accelerated, the paint film becomes rough and loose; the solid content is too low, the throwing power is decreased, the electrodeposition effect is poor, the paint film is thin and pinholes and orange peel are easily generated.
3.7 Yan Jibi
Yan Jibi indicates the ratio of pigment to resin in the heating residue (or dry film) of the electrophoretic coating. The difference in the pigment base ratio will affect the appearance quality and corrosion resistance of the film.
3.8 solvent content
The amount of hydrophilic organic solvent contained in the electrophoresis bath liquid, the solvent content affects the solubility of the paint, and thus affects the quality of the paint film.
3.9 baking temperature and time
Electrophoretic drying time and temperature are very important. If the minimum time and temperature are not reached, the paint film on the swimming coating will not cure well, which will seriously affect the hardness, impact resistance and corrosion resistance of the paint film. .
4, the conclusionIn summary, the above-mentioned anodic electrophoresis process parameters are scientifically managed and periodically tested, and adjusted according to the test results, which is a basic requirement for making full use of existing process equipment and maximizing the production of qualified satellite receiving antennas.
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